The proband, a woman in her late forties, had endured recurrent episodes of non-pitting edema affecting her face, extremities, and abdomen since her mid-teens. The attacks, estimated at fifteen to twenty per year, each lasted two to four days, occurred without the hives that characterize allergic swelling, and stubbornly resisted antihistamines, glucocorticoids, and even epinephrine. She had never taken the medications most often implicated in drug-induced angioedema, including angiotensin-converting enzyme inhibitors, angiotensin-receptor blockers, dipeptidyl peptidase-4 inhibitors, or exogenous estrogens. Crucially, she also carried a diagnosis of systemic lupus erythematosus made in adolescence, though the disease had remained clinically quiescent on stable low-dose prednisolone, with no recent flares, significant proteinuria, serositis, or active mucocutaneous disease.

Laboratory testing performed in both 2020 and 2022 painted a picture that seemed, at first glance, unambiguous. Her C4 levels sat persistently at 3.0 milligrams per deciliter, far below normal. Her C1-inhibitor antigen levels measured 7 and then 5 milligrams per deciliter, with functional activity of 31 percent and then less than 25 percent — a pattern classic for type 1 C1-inhibitor deficiency, in which the protein is both quantitatively reduced and functionally impaired. But then came the anomaly: C1q was undetectable at both time points, falling below the assay’s detection limit of 1.5 milligrams per deciliter on each occasion.

That finding should have pointed decisively toward acquired angioedema. In the hereditary form of the disease, C1q is typically normal, because the genetic defect impairs only the C1-inhibitor protein itself, leaving the rest of the classical complement pathway largely intact. In the acquired form, by contrast, consumption or autoimmune destruction of C1-inhibitor triggers runaway activation of the classical pathway, dragging C1q down with it. Profoundly low C1q has therefore long been regarded as one of the most reliable biochemical fingerprints separating the two conditions. Faced with an undetectable C1q in a middle-aged woman, the clinical team reasonably worried that an acquired process — potentially signaling an underlying lymphoproliferative disorder or monoclonal gammopathy — was hiding beneath the surface.

The initial workup, however, came back clean. Serum protein electrophoresis with immunofixation revealed no monoclonal protein, and computed tomography showed no lymphadenopathy. Anti-C1q antibodies, anti-C1-inhibitor antibodies, and sequencing of the SERPING1 gene — the gene whose mutations cause hereditary angioedema type 1 and type 2 — had not yet been performed at the time of publication, and the authors are careful to acknowledge that they cannot claim definitive exclusion of acquired disease. What they could do, and what ultimately proved decisive, was something far simpler and more powerful: test the family.

Five biologically related individuals spanning three generations, including members of a collateral line, underwent repeat complement testing. The results were striking in their internal consistency. The proband’s son, sister, niece, and father all showed reproducibly low C4 alongside low C1-inhibitor antigen and function — the biochemical signature of type 1 hereditary angioedema — yet none of them had lupus. And their C1q values told a completely different story from the proband’s. The son’s C1q measured 14.7 and then 13.8 milligrams per deciliter; the sister’s, 10.1 and then 11.0; the niece’s, 12.4 and then 10.7 — all comfortably within reference ranges. Only the father showed subnormal C1q at 6.9 and then 6.1 milligrams per deciliter, but his position within a multigenerational pedigree carrying the same C1-inhibitor defect still argued strongly for hereditary transmission rather than an independent acquired process.

The overall pattern, the authors conclude, was not acquired angioedema with low C1q, but familial C1-inhibitor deficiency with discordant C1q values — with the most extreme reduction confined to the one family member who also had systemic lupus erythematosus. This distinction is far from academic. Hereditary angioedema and lupus have been reported together before, and their coexistence can complicate complement interpretation in ways that clinicians may not anticipate. Low serum C1q can arise from multiple distinct mechanisms: inherited C1q deficiency, immune-complex-mediated consumption of the classical pathway as seen in active lupus, hypocomplementemic urticarial vasculitis, or cryoglobulinemic vasculitis, and acquired C1-inhibitor deficiency associated with monoclonal gammopathy, lymphoproliferative disease, or autoimmunity. In this patient, the absence of severe childhood infections, urticarial vasculitis-like lesions, cryoglobulinemic features, monoclonal protein, or lymphadenopathy made most alternatives unlikely, leaving overlapping lupus as the most plausible driver of her extreme C1q reduction.

The clinical stakes of getting this right are considerable. Labeling the proband as having acquired angioedema on the basis of C1q alone would have contradicted her adolescent onset, a clear three-generation familial pattern, and repeated concordant deficiency of C1-inhibitor antigen and function in her relatives. It would also have redirected her clinical care toward surveillance for hematologic malignancy rather than management of a lifelong genetic condition with well-established treatment pathways. Conversely, the authors emphasize, a low C1q result should never simply be ignored. It justifies structured surveillance and confirmatory testing, particularly because acquired C1-inhibitor deficiency can be associated with monoclonal gammopathy and hematologic disease that require their own monitoring and intervention.

The report also extends an earlier family description published by the same group, adding two new dimensions: serial C1q measurements across all tested relatives, and direct demonstration that profound C1q reduction can coexist with hereditary C1-inhibitor deficiency in a patient with overlapping lupus. The principal limitation remains the absence of molecular and autoantibody confirmation — SERPING1 sequencing and anti-C1-inhibitor antibody testing are still pending. Even so, the most parsimonious interpretation, the authors argue, is hereditary type 1 C1-inhibitor deficiency with lupus-associated or immune-mediated C1q reduction in the proband, rather than acquired angioedema diagnosed on the strength of a single complement value.

The broader lesson for clinicians managing recurrent angioedema is one of disciplined humility toward individual biomarkers. In patients with recurrent swelling — especially when onset is early and family clustering is evident — very low C1q should trigger a thorough confirmatory evaluation for acquired disease, but it should never be allowed to override a hereditary pattern revealed by age at onset, family history, and repeated testing of relatives. Complement biology, like the patients it serves, rarely obeys a single number.

Subject of Research: Diagnostic pitfalls of low C1q in distinguishing hereditary from acquired C1-inhibitor deficiency angioedema in a family with overlapping systemic lupus erythematosus

Article Title: Low C1q alone should not be taken as diagnostic of acquired angioedema in a kindred with familial type 1 C1-inhibitor deficiency and overlapping systemic lupus erythematosus

Article References: Takagi, A., Takamura, S., & Fukuda, T. (2026). Low C1q alone should not be taken as diagnostic of acquired angioedema in a kindred with familial type 1 C1-inhibitor deficiency and overlapping systemic lupus erythematosus. Journal of Cutaneous Immunology and Allergy, 9, Article 16999. https://doi.org/10.3389/jcia.2026.16999

Image Credits: AI Generated

DOI: 10.3389/jcia.2026.16999

Keywords: hereditary angioedema, acquired angioedema, C1-inhibitor deficiency, C1q, systemic lupus erythematosus, complement system, C4, SERPING1, family testing, monoclonal gammopathy, biomarker interpretation, immunology

The scientific rationale is compelling. IgA nephropathy follows a multi-hit pathogenic sequence that begins with the production of galactose-deficient IgA1, an abnormally glycosylated antibody. Anti-glycan antibodies bind this molecule to form circulating immune complexes that deposit in the mesangium, the connective tissue scaffolding of the glomerulus. There they trigger local inflammation, predominantly by activating the alternative and lectin complement pathways, with limited evidence for classical pathway involvement. The alternative pathway is considered the dominant amplifier: it is constantly active at low levels in the circulation and can be enhanced by the deposited immune complexes. The lectin pathway, driven by pattern-recognition molecules such as mannan-binding lectin and ficolins that bind directly to the deposits, activates MASP-2 and downstream cleavage of complement components, adding a second engine of glomerular injury.

Both pathways converge at C3, generating the effector molecules C3a and C5a, which recruit inflammatory cells and promote cytokine release, and the membrane attack complex C5b-9, which drives mesangial cell proliferation, oxidative stress and extracellular matrix expansion. Persistent complement activation may also damage the endothelium: several studies have found histological evidence of thrombotic microangiopathy in a subset of patients, particularly severe cases, suggesting an additional injury mechanism that could explain the clinical heterogeneity of the disease. Precisely because complement sits at the center of this pathology, its proteins have become the most closely watched candidate biomarkers in nephrology, especially now that drugs designed to shut down specific complement pathways have reached the clinic.

Among tissue markers, mesangial C4d has emerged as the most extensively studied. Deposits of lectin pathway components are found in roughly 25 to 50 percent of IgA nephropathy biopsies, usually without C1q, supporting lectin pathway involvement. A meta-analysis of 12 studies including 1,251 participants reported an overall prevalence of glomerular C4d deposition of 34 percent. Multiple investigations have shown that C4d-positive patients have greater proteinuria, lower kidney function and adverse Oxford MEST lesions, including mesangial hypercellularity and segmental sclerosis, and deposition has been reported as an independent predictor of progression. Yet C4d has not entered standard risk models, and because lectin pathway activation occurs only in a subset of patients, its relevance to the global population remains unclear.

In the circulation, the factor H-related protein family has attracted particular attention. These proteins, encoded at the complement factor H gene locus, can compete with factor H, the major negative regulator of C3 activation. Plasma FHR-1 is elevated in patients even when kidney function is normal, and the FHR-1 to factor H ratio, proposed as a better measure of the balance between complement control and dysregulation, is significantly raised in patients with progressive disease. FHR-5 tells a different story: it does not track progression but correlates with more severe histological features and a reduced response to immunosuppression, hinting at a role in predicting treatment response. Alternative pathway cleavage products Bb and Ba also carry prognostic weight, with higher Bb linked to vascular and tubular lesions and worse long-term outcomes, while plasma Ba falls after immunosuppression. Low circulating MASP-3, meanwhile, has consistently marked severe, progressive disease.

Conventional serum measures are finding new life as well. In a study of 1,356 Chinese patients, serum C4 correlated with proteinuria, kidney function and the extent of chronic damage, and elevated levels were an independent risk factor for progression. The C3/C4 ratio outperformed either protein alone in predicting poor clinical and pathological features, and in a recent report the addition of serum C3 and C4 improved the predictive performance of both the CKD progression model and the International IgAN Risk Prediction Tool. The IgA/C3 ratio has shown strong diagnostic and prognostic associations in Asian cohorts, but inconsistent results elsewhere mean its generalizability remains unresolved.

Urine offers a non-invasive window onto intrarenal inflammation. Elevated urinary C4d has been associated with greater proteinuria, more severe histopathological injury and increased progression risk, independent of conventional factors, and with poorer response to steroids. Urinary factor H and soluble C5b-9 correlate with proteinuria, interstitial fibrosis and glomerulosclerosis, and a Swedish cohort found that urinary pentraxin 3 and mannan-binding lectin tracked active proliferative lesions while C4c marked chronic fibrosis and faster function decline. A caution remains: most studies lacked proteinuria-matched control groups, so urinary complement may partly reflect nonspecific leakage across a damaged filtration barrier rather than disease-specific activation.

The therapeutic stakes of these measurements are now enormous. The oral factor B inhibitor iptacopan, which suppresses the alternative pathway, reduced proteinuria and slowed kidney function loss in phase 2 and 3 trials, with the final 24-month APPLAUSE-IgAN data showing an annualized total eGFR slope of minus 3.10 versus minus 6.12 ml/min/1.73 m² per year compared with placebo and a kidney-failure endpoint hazard ratio of 0.57. Iptacopan received accelerated FDA approval in 2024 and traditional approval in 2026. The antisense oligonucleotide sefaxersen cut factor B, Bb and urinary Ba while reducing proteinuria by roughly 43 percent in phase 2 and now advances in a phase 3 program. Terminal pathway blockade also works: ravulizumab reduced proteinuria by 30.1 percent versus placebo at week 26, and the siRNA agent cemdisiran achieved a placebo-adjusted 37.4 percent reduction, although it has not progressed to phase 3. By contrast, the MASP-2 inhibitor narsoplimab failed its phase 3 program, a result that highlights the heterogeneity of complement activation and the potential need for biomarker-guided patient selection.

Despite this momentum, the review is candid about the gaps. The KDIGO 2025 guideline states that apart from proteinuria and eGFR there are no validated prognostic serum or urine biomarkers for IgA nephropathy, even while flagging biomarker discovery as a high-priority research recommendation. Most candidate markers have been evaluated in single-center studies with differing assays, non-standardized cut-offs and heterogeneous outcome definitions, yielding moderate and inconsistent performance. Each compartment has inherent limitations: biopsies provide the most direct evidence of complement activation but are invasive and unsuited to repeated monitoring; circulating markers are accessible but may reflect systemic rather than kidney-specific activation; urinary markers are promising but remain largely unvalidated. Complement activation also differs across ethnic populations and may shift over the course of disease.

The authors argue that the field’s priority should now shift from proving that complement matters to identifying which patients benefit most from which inhibitor, guided by pathway-specific biomarkers. The principle they invoke is straightforward: right pathway, right drug, right patient, right time. Biomarker-driven stratification could match pathway activity to targeted therapy, minimize unnecessary immunosuppression and reduce adverse effects, and may eventually reveal whether patients with complement-mediated thrombotic microangiopathy, a phenotype so far studied only in case reports, derive special benefit from complement inhibition. Large, multiethnic, longitudinal studies will be needed before complement biomarkers can move from research tool to routine clinical practice, but with effective complement drugs already approved, the incentive to validate them has never been greater.

Subject of Research: Complement biomarkers for diagnosis, prognosis and complement-targeted therapy in IgA nephropathy

Article Title: Complement biomarkers in IgA nephropathy: current insights and clinical relevance

Article References: Balmukhanova, A., Chan, C. E., & Barratt, J. (2026). Complement biomarkers in IgA nephropathy: current insights and clinical relevance. Frontiers in Nephrology, 6, Article 1918450. https://doi.org/10.3389/fneph.2026.1918450

Image Credits: AI Generated

DOI: 10.3389/fneph.2026.1918450

Keywords: IgA nephropathy, complement system, biomarkers, C4d, alternative pathway, lectin pathway, iptacopan, kidney disease, glomerulonephritis, precision medicine, proteinuria, nephrology

The decision to focus on complement biology rather than the motor neurons themselves reflects a significant shift in how researchers conceptualize amyotrophic lateral sclerosis. For much of the modern era, therapeutic development treated ALS as a straightforward problem of neuronal survival, screening compounds for their ability to keep motor neuron cell bodies alive in laboratory dishes. Yet post-mortem tissue analysis and longitudinal imaging studies in patients have consistently shown that synaptic connections begin to unravel long before large numbers of neurons disappear. This means the window during which intervention can meaningfully preserve function is dominated by processes at the synapse and the neuromuscular junction, structures that operate as the critical relay between the nervous system and skeletal muscle. When those relays fail, muscle fibers are denervated, atrophy follows, and the compensatory sprouting responses that initially mask weakness eventually collapse.

The complement system offers a particularly compelling mechanistic explanation for this early synaptic loss. Originally characterized as a cascade of circulating proteins that tags bacteria and damaged cells for destruction, complement has more recently been recognized as an active participant in brain circuit refinement. During normal development, astrocytes and microglia use complement signals such as C1q and C3 to identify synapses that should be pruned, sculpting neural networks into their mature configurations. In neurodegenerative disease, this developmental program appears to be inappropriately reawakened in adult tissue, with mature, functional synapses mistakenly carrying the same molecular tags intended for transient or damaged connections. Microglia, armed with complement receptors, then engulf these tagged synapses in a process that resembles immunologically sanctioned amputation of healthy circuitry.

Previous genetic and pharmacological studies in ALS models have supported this framework. Mice lacking certain complement components show delayed disease onset and extended survival in some genetic backgrounds, while elevated levels of C1q, C3 degradation products, and the anaphylatoxin C5a have been measured in spinal cord tissue from both patients and SOD1-mutant animals. The inflammatory amplification loop mediated by C5a and its receptor C5aR1 has attracted particular attention because C5a is one of the most potent chemoattractants produced during complement activation, drawing immune cells into sites of pathology and stimulating them to release cytokines and reactive oxygen species. Blocking this axis alone, however, leaves the upstream tagging machinery untouched, which may explain why single-node complement interventions have produced inconsistent results across different preclinical studies.

The dual-targeting strategy described in this study therefore carries conceptual weight beyond the specific properties of atovaquone. By simultaneously engaging C1qb, a core structural component of the C1q recognition complex that initiates classical pathway deposition, and C5aR1, the receptor that amplifies downstream inflammation, the intervention addresses both the initiation and the propagation of complement-driven injury. This is analogous to combination approaches in other therapeutic domains, where inhibiting an upstream trigger alongside a downstream amplifier produces more durable suppression of a pathological cascade than either node alone. Whether this dual engagement translates into superior outcomes over monotherapies targeting a single complement component will require careful head-to-head testing, but the pharmacological logic is sound.

The identification of atovaquone as a candidate complement modulator emerged from computational screening rather than from traditional medicinal chemistry, illustrating how virtual docking has become a productive entry point for drug repurposing. Molecular docking algorithms predict binding poses and approximate affinities between small molecules and protein structures, allowing researchers to survey thousands of approved compounds for activity against targets of interest at a fraction of the cost of experimental screening. The prediction that atovaquone binds both C5aR1 and C1qb was then substantiated with surface plasmon resonance, a biophysical technique that measures real-time binding between immobilized proteins and flowing analytes, providing kinetic parameters that docking alone cannot supply. This layered validation approach, moving from computational prediction to direct physical measurement, strengthens confidence that the observed biological effects arise from the proposed molecular interactions rather than incidental pharmacology.

Atovaquone itself has an intriguing pharmacological history relevant to neurodegenerative applications. The drug acts as a mitochondrial electron transport inhibitor in parasites, disrupting the cytochrome bc1 complex at the parasite’s cytochrome b gene product. This mitochondrial mechanism has drawn interest in unrelated contexts, because mitochondrial dysfunction is a well-documented feature of ALS, and some investigators have explored whether atovaquone’s effect on mitochondrial respiration could induce a mild protective metabolic shift in mammalian cells. The present study adds complement modulation to this repertoire, suggesting that the compound may act through several converging pathways rather than a single mechanism. Such pleiotropy can be a liability in precision pharmacology but an asset in complex multifactorial diseases like ALS, where no single lesion accounts for the full phenotype.

The delivery problem the researchers confronted is central to why many promising CNS drug candidates fail in translation. The blood-brain barrier and the blood-spinal cord barrier are specialized endothelial assemblies with tight junctions, efflux transporters, and restrictive paracellular permeability that exclude the vast majority of circulating molecules. Atovaquone is highly lipophilic and poorly water-soluble, which complicates formulation and tends to limit systemic exposure after oral administration. For an ALS therapy, delivery must additionally reach the spinal cord, where anterior horn motor neurons and their axons constitute the principal site of pathology, and the barriers guarding spinal tissue are at least as restrictive as those protecting the brain. Achieving therapeutic concentrations at these lesion sites is therefore a substantial formulation challenge, not merely a matter of increasing dose.

Lactoferrin offers a rational solution rooted in endogenous biology. This iron-binding glycoprotein, abundant in secretions and neutrophil granules, is recognized by lactoferrin receptors expressed on the endothelial cells of CNS barriers, where it participates in receptor-mediated transcytosis, the process by which cargo is ferried across the barrier cell from the blood side to the tissue side. Conjugating or incorporating lactoferrin into a nanoparticle shell effectively hitchhikes on this transport pathway. In the formulation described here, lactoferrin forms a hydrophilic exterior that stabilizes the particle in aqueous biological fluids, while atovaquone molecules aggregate in a hydrophobic core, sidestepping the solubility problem that limits conventional dosing. Nanomicelle formulations of this general type have been explored extensively in cancer and infectious disease drug delivery, and their adaptation for neurodegenerative indications represents a growing area of pharmaceutical science.

Characterization of such nanomedicines requires rigorous attention to physical parameters that determine biological behavior. Particle size influences both circulation half-life and the tendency to accumulate in particular tissues, with particles in the tens to low hundreds of nanometers generally favored for passive and receptor-mediated tissue penetration. Surface charge affects protein adsorption and immune recognition, while stability in serum determines whether the payload reaches its destination or precipitates prematurely. The authors report verification of these properties along with direct measurement of spinal-cord enrichment in vivo, an essential step because many nanocarriers that perform well in benchtop assays fail to deposit meaningful quantities of drug in central nervous tissue. Quantitative confirmation of delivery, ideally with spatial resolution showing accumulation in regions of active pathology, distinguishes credible CNS nanotherapy studies from those resting on indirect pharmacodynamic readouts alone.

The experimental design integrating human transcriptomic data, single-cell RNA sequencing, in vitro inflammatory models, and the SOD1-G93A mouse reflects the multi-scale approach now considered standard for preclinical neurodegeneration research. Single-cell analysis is particularly valuable in ALS because the disease involves a complicated choreography among neurons, astrocytes, microglia, oligodendrocytes, and infiltrating peripheral immune cells, each of which responds differently to treatment. Resolving complement gene expression at the level of individual cell populations allows the investigators to confirm that the pathological signatures they target are indeed present in the relevant cellular compartments rather than diluted into bulk tissue averages. Similarly, the use of both BV2 microglial cells and NSC34 motor neuron-like cells provides parallel perspectives on the inflammatory and neuronal sides of the disease process.

Caution remains warranted before extrapolating these findings to patients. The SOD1-G93A mouse, though historically indispensable, reproduces a rare familial form of ALS and has a mixed record predicting clinical success; therapies that extended survival in this model, including several approved drugs, showed modest or negligible benefit in human trials dominated by sporadic cases with heterogeneous underlying mechanisms. Complement activation is, however, one of the pathological features shared across multiple ALS genetic subtypes, which strengthens the argument that complement-targeted approaches may generalize beyond SOD1 mutation carriers. Independent replication in additional models, including TDP-43 and C9orf72 transgenic lines, and eventually in biomarker-rich patient cohorts, will be necessary to establish clinical relevance.

The translational advantages of repurposing an approved drug should not be underestimated. Atovaquone already possesses an established human safety profile, known pharmacokinetics, recognized drug interactions, and existing manufacturing infrastructure, all of which compress the development timeline compared with novel chemical entities. Combined with a delivery system designed specifically for spinal-cord access, the approach addresses two of the most common reasons ALS drug candidates fail: inadequate exposure at the site of disease and mechanisms that engage only one facet of a multifactorial pathology. If subsequent studies confirm that complement suppression in the spinal cord correlates with preserved neuromuscular junction integrity and slowed functional decline, this nanomedicine strategy could provide a template for repositioning other approved compounds against complement-driven neurodegeneration in ALS and related disorders.

Subject of Research: ALS nanotherapy

Article Title: A CNS-targeted atovaquone nanotherapy mitigates complement activation and neuromuscular degeneration in ALS

Article References: Ding, Y.-N., Bahati, M., Li, M.-Q., Guan, P.-P., & Wang, P. (2026). A CNS-targeted atovaquone nanotherapy mitigates complement activation and neuromuscular degeneration in ALS. Materials Today Bio, 41, Article 103738. https://doi.org/10.1016/j.mtbio.2026.103738

Image Credits: AI Generated

DOI: 10.1016/j.mtbio.2026.103738

Keywords: ALS, atovaquone, drug repurposing, complement system, lactoferrin, nanomicelles, SOD1-G93A mice, neuroinflammation, neuromuscular junction, C5aR1, C1qb, spinal cord delivery

At birth, both the innate and adaptive arms of immunity are functionally incomplete. Newborns depend heavily on maternal antibodies transferred across the placenta for passive protection, and this shield decays within months: estimated durations of maternal antibody protection are roughly 3.3 months for measles, 2.7 months for mumps, 3.9 months for rubella, and 3.4 months for varicella. Neonates can mount adaptive responses, but their capacity to generate long-lasting immunity is limited by underdeveloped germinal centers, low expression of B-cell co-receptors such as CD21, CD40, CD80, and CD86, impaired Th1 cytokine secretion, and reduced B-cell receptor signaling strength. The review emphasizes that this is not simple deficiency. The neonatal immune system operates in a tolerogenic mode, likely to prevent immunopathological damage as the infant transitions from a semi-allogeneic, sterile uterine environment into a microbe-rich world, even at the cost of vulnerability to uncontrolled pathogen proliferation.

The innate immune system, the first line of defense, is active from birth and responds within minutes to hours, but its cellular players mature on very different schedules. Neutrophils appear in fetal circulation by the end of the first trimester and surge before delivery, yet neonatal neutrophils show weak inflammatory responses, a deficit most pronounced in premature infants. Monocytes and macrophages in newborns exhibit diminished signaling and cytokine responses compared with adults, reaching normal levels within days. Crucially, the review highlights the newborn microbiome as the first teacher of the developing immune system: gut microbes induce interleukin-17 production by group 3 innate lymphoid cells, which drives granulocyte colony-stimulating factor release and neutrophil production through a Toll-like receptor 4 and MyD88-dependent pathway, maintaining systemic immune vigilance against infection.

Dendritic cells, the sentinels that bridge innate and adaptive immunity, tell a similarly staged story. Plasmacytoid dendritic cells, the body’s type I interferon factories against viruses, constitute 53 percent of the dendritic cell pool in infants, the lowest total dendritic cell proportion of any age group. Although preterm infants possess adult-like levels of TLR7 and TLR9 on these cells, they secrete low amounts of interferon-alpha and beta, leaving antiviral innate immunity ineffective relative to adults. A progressive increase in conventional dendritic cell subsets occurs during the transition from infancy to childhood, suggesting major immune remodeling early in life. In older adults, the dominant subset is cDC2 at 49 percent, while cDC1 cells expand preferentially in adulthood, possibly compensating for the age-related decline in CD8-positive T cells. Lower plasmacytoid dendritic cell proportions in healthy older people may partly explain their reduced capacity to fight viral infections.

Natural killer cells and other innate lymphoid populations undergo their own lifelong remodeling. Newborn natural killer cells have reduced cytolytic function, blunted sensitivity to interleukin-2 and interleukin-15, and lower interferon-gamma secretion, yet still provide some antiviral protection. During pregnancy, maternal peripheral natural killer cells migrate to the decidua and differentiate into non-cytotoxic cells with enhanced secretory activity, producing interferon-gamma, vascular endothelial growth factor, and placental growth factor that are critical for immune tolerance, angiogenesis, and fetal development, though their hyperactivation can trigger spontaneous abortion. With age, natural killer cells shift toward a mature CD56dimCD16-positive phenotype but become dysfunctional in cytotoxicity, degranulation, and cytokine secretion, weakening the elimination of senescent and malignant cells. Strikingly, single-cell RNA sequencing of three centenarian cohorts revealed increased peripheral natural killer cell frequencies in these exceptionally long-lived individuals, alongside reduced CD4-positive T and B cell counts.

That centenarian signature has crystallized into one of the review’s central themes: cytotoxic immunity as a marker of healthy aging. A bioinformatic algorithm developed to identify immune populations associated with longevity found that natural killer cells, CD8-positive T cells, and gamma-delta T cells correlate positively with extended lifespan, whereas inflammatory-lineage populations such as CD4-positive T cells, B cells, and dendritic cells show negative associations. Centenarian neutrophils display phagocytic and chemotactic activities comparable to those of young adults, with low superoxide anion levels and preserved glutathione, while frail middle-aged subjects show the worst profiles. Reduced complement C3 and C4 levels in centenarians contrast with the elevated levels seen in older adults at risk of metabolic syndrome and cardiovascular disease, and caloric restriction has been shown to downregulate the C3a/C3 ratio, attenuating age-related inflammation. Maintaining cytotoxic phenotypes and redox balance, the authors suggest, may be exploitable clinically to blunt immunosenescence.

The adaptive arm follows an equally dramatic arc. T lymphocytes mature in the thymus from seven to eight weeks of gestation and populate the periphery by weeks twelve to thirteen, but thymic involution drives a progressive loss of naive T cells that accelerates after age sixty. Newborns carry only about 1 percent antigen-educated T cells; in adults over sixty, that figure reaches 65 percent. The T cell receptor repertoire narrows with age, CD28 expression is lost from more than half of CD8-positive T cells, and transcriptional reprogramming pushes aging T cells toward a Th2 polarization associated with dysregulated B cell responses and reduced antibody neutralizing capacity after influenza vaccination, a failure that contributes to influenza deaths in 70 to 85 percent of elderly cases. B cells, meanwhile, peak in the first year of life at around six months before gradually declining, and in old age naive B cells are replaced by quiescent memory cells with diminished affinity maturation and class switching.

Perhaps the most conceptually provocative section concerns immunological memory itself. Long considered the exclusive property of adaptive immunity, memory-like responses have now been demonstrated in innate cells, a phenomenon termed trained immunity. Monocytes, macrophages, natural killer cells, and even bone marrow progenitors exposed to stimuli such as beta-glucan or the Bacillus Calmette-Guerin vaccine undergo epigenetic and metabolic reprogramming that confers enhanced, non-antigen-specific protection against unrelated pathogens for months. In murine models, BCG vaccination at birth improved survival in neonatal sepsis with profound remodeling of monocyte and neutrophil subsets, though some pattern recognition receptor agonists failed to protect neonatal mice against Leptospira, underscoring the risks of immunostimulation in early life. In adults over fifty in Guinea-Bissau, BCG vaccination elevated interferon-gamma and pro-inflammatory cytokine responses two months later, and some reports suggest it can reduce circulating inflammatory markers of inflammaging, although recent large trials found no boost to influenza vaccine responses and even flagged aggravation of cardiac arrhythmias as a concern.

The demographic stakes are considerable. The World Health Organization estimates that people over sixty numbered 1.2 billion in 2025 and will reach 2 billion by 2050, with 80 percent living in developing countries, while the European Union’s elderly share is projected to grow from 6.0 percent in 2021 to 14.6 percent by 2100. Immunosenescence, driven by thymic involution, naive cell depletion, inverted CD4/CD8 ratios, gut microbiota shifts that increase intestinal permeability, and the accumulation of senescent cells secreting interleukin-6, tumor necrosis factor-alpha, and interleukin-1 beta, raises vulnerability to infections, cancer, autoimmune disease, and neurodegeneration. Yet the aging immune system paradoxically resembles the newborn’s, with weakened antimicrobial activity and compromised adaptive responses at both ends of life. The Bucharest team argues that mapping these stage-specific mechanisms, from the SOX4-positive naive T cells and interferon-gamma that compensate for infant vulnerability to the cytotoxic dominance that defines centenarian immunity, provides the mechanistic foundation for age-adapted vaccines and immunotherapies capable of restoring immune function in the frail and extending healthy lifespan for everyone else.

Subject of Research: Immune system development across the human lifespan, from neonatal immaturity to immunosenescence and centenarian longevity

Article Title: Immune system ontogeny—a subtle evolution to perfection

Article References: Munteanu, A. N., Surcel, M., Dobre, E. G., Constantin, C., & Neagu, M. (2026). Immune system ontogeny—a subtle evolution to perfection. Frontiers in Aging, 7, Article 1872955. https://doi.org/10.3389/fragi.2026.1872955

Image Credits: AI Generated

DOI: 10.3389/fragi.2026.1872955

Keywords: immunosenescence, inflammaging, trained immunity, neonatal immunity, centenarians, natural killer cells, dendritic cells, T cells, B cells, immunological memory, complement system, BCG vaccine

C4d is a degradation fragment of the complement protein C4b, generated when the classical complement pathway is activated. In ABO-compatible kidney transplantation, peritubular capillary C4d deposition follows the binding of anti-HLA donor-specific antibodies and is recognized as a histological hallmark of antibody-mediated injury and poor prognosis. In ABO-incompatible grafts, however, the picture is strikingly different. C4d appears in the peritubular capillaries of more than half of recipients, yet most of these grafts function well for years. This paradox has been attributed to endothelial accommodation, a state in which membrane-bound complement regulatory proteins such as CD46, CD55, and CD59 restrain complement-mediated injury on the graft endothelium despite ongoing antibody binding. The clinical significance of C4d deposition in this setting has remained unclear, and most previous studies evaluated it at only a single time point.

The Tokyo team, led by Yu Kijima and colleagues, took a different approach. Because a single determination may not reflect a sustained process, they defined C4d positivity by its persistence across two sequential post-transplant protocol biopsies, obtained at 3 months and 1 year after surgery. Between 2015 and 2022, their center performed 254 ABO-incompatible kidney transplantations, and 69 recipients with paired protocol biopsies formed the study population. Fifty-four recipients, or 78.3 percent, were classified as persistently C4d-positive, meaning C4d deposition was detectable in both biopsies, while 15 recipients were classified as C4d-negative or nonpersistent. The researchers then compared pre-transplant background characteristics, cellular infiltration, chronic Banff lesions according to the Banff 2019 classification, graft function, and graft survival between the two groups.

The immunosuppressive regimen itself is worth noting for its technical sophistication. Patients received a triple-drug protocol consisting of tacrolimus, mycophenolate mofetil, and methylprednisolone, starting seven days before transplantation, with tacrolimus doses adjusted to trough levels of 8 to 12 nanograms per milliliter during the first month. Induction with the anti-IL-2 receptor antibody basiliximab was performed in all recipients, and all patients received low-dose rituximab for B-cell depletion, which has replaced splenectomy at the center since 2004. Before surgery, recipients underwent three or four sessions of double-filtration plasmapheresis to remove anti-A and anti-B antibodies until titers fell to 1:32 or below. Recipients who received intravenous immunoglobulin at induction were excluded from the analysis because IVIG may inactivate activated complement and thereby influence C4d deposition.

The biopsy protocol was equally rigorous. Renal allograft biopsies were obtained at time zero as a back-table biopsy, at 3 months, and at 1 year, with an adequate specimen defined as one containing seven or more glomeruli and at least one arterial cross-section. C4d staining was performed by indirect immunofluorescence on cryostat sections using a mouse monoclonal anti-human C4d antibody, scored from 0 to 3 according to Banff criteria ranging from no staining to diffuse staining of more than half of the peritubular capillaries. The persistent C4d-positive group included recipients with deposition at both time points, even when the staining score was a reproducible low-grade 1 at both visits. As a sensitivity analysis, the team also repeated all comparisons using a stricter, Banff-concordant definition requiring a C4d score of at least 2 at both time points, which yielded 47 positive and 22 negative recipients and did not change the overall pattern of findings.

The results were largely reassuring. Baseline anti-A and anti-B antibody titers, ABO donor-recipient combinations, donor age, and donor relationship did not differ between the groups, although donor sex did, with a higher proportion of male donors in the C4d-positive group, a finding the authors attribute cautiously to chance given the number of comparisons performed. Microvascular inflammation, defined as a combined glomerulitis plus peritubular capillaritis score of 2 or more, was observed in 6 of 54 persistently C4d-positive recipients, or 11.1 percent, versus 1 of 15, or 6.7 percent, in the negative group. Chronic changes, defined as an interstitial fibrosis score of at least 1, appeared in 27 of 54, or 50.0 percent, versus 6 of 15, or 40.0 percent. None of these differences reached statistical significance, and cellular infiltration scores for interstitial inflammation, tubulitis, glomerulitis, and peritubular capillaritis were similarly comparable at both time points.

Graft function and survival told the same story at the group level. Serum creatinine at 1 year did not differ significantly between the groups, nor did estimated glomerular filtration rate, which measured a median of 45.5 versus 43.6 milliliters per minute per 1.73 square meters. Kaplan-Meier analysis showed no significant difference in graft survival, with a log-rank P value of 0.191, and this conclusion held in a landmark analysis with the time origin at the 1-year biopsy, designed to address the guarantee-time bias inherent in requiring a 1-year biopsy for group assignment. Biopsy-proven rejection was infrequent in both groups: nine episodes were identified among the 69 recipients, seven in the C4d-positive group and two in the negative group, including cases of borderline change, active and chronic active antibody-mediated rejection, and chronic active T-cell-mediated rejection.

Yet one finding refuses to be dismissed. All four graft losses in the analyzed cohort occurred in the persistent C4d-positive group, occurring at 1,849, 1,926, 2,231, and 3,208 days after transplantation. Three of the four were ultimately attributable to chronic active antibody-mediated rejection, and the fourth to BK virus nephropathy. Critically, these cases were not homogeneous. One recipient had biopsy-confirmed chronic active antibody-mediated rejection with a microvascular inflammation score of 3 at the very 1-year protocol biopsy used to define C4d persistence, meaning early persistent C4d was accompanied by concurrent histological injury. In the remaining two rejection cases and the BK virus case, no microvascular inflammation or overt rejection was present on either the 3-month or 1-year biopsies, and the chronic active antibody-mediated rejection was diagnosed later, at 1.9 years post-transplant in one case and at an undetermined later time in the other. This heterogeneity suggests that persistent C4d at 3 months and 1 year does not reliably distinguish recipients who will remain stable from those who will later develop overt humoral injury.

A parallel signal emerged in the antibody data, though with important caveats. Post-transplant donor-specific antibody testing was available for 47 of the 69 recipients, and de novo donor-specific antibodies were detected in 11 of 38 evaluable recipients, or 28.9 percent, in the C4d-positive group, compared with 1 of 9, or 11.1 percent, in the negative group. This difference did not reach statistical significance, and the authors emphasize that it is exploratory at best: testing was not performed at uniform time points, measurements spanned roughly 4 months to 3 years after transplantation, and the 22 recipients without available data had significantly shorter follow-up. Whether persistent C4d deposition is unrelated to subsequent HLA sensitization or reflects low-grade humoral activity that could contribute to later sensitization simply cannot be determined from this retrospective cohort, and the absence of molecular transcript profiling further limited the ability to detect subclinical humoral activity.

The authors are admirably candid about the limits of their work. The study was retrospective and single-center, and the comparator group of only 15 patients left it substantially underpowered for low-frequency endpoints such as rejection and graft loss, meaning the null results represent a failure to detect an association rather than evidence of equivalence. The cohort was also highly selected: only 69 of 254 recipients qualified, with exclusions for insufficient pathological data, prior treated rejection, thrombotic microangiopathy, IVIG induction, retransplantation, and recurrent glomerular disease effectively removing the higher-risk population. Anti-A/B titers were available only before transplantation, so the researchers could not determine whether persistent C4d reflected ongoing antibody exposure with successful accommodation or merely residual complement footprints. Taken together, the findings are consistent with accommodation but hypothesis-generating rather than definitive, and the authors call for confirmation in larger, prospective cohorts with systematic de novo donor-specific antibody surveillance and molecular diagnostics. For now, the message for clinicians is nuanced: persistent C4d in an ABO-incompatible graft is not by itself a cause for alarm, but the small cluster of late losses in the positive group suggests that long-term immunological surveillance, rather than either reassurance or immediate treatment escalation based on early biopsies alone, may be the wisest course.

Subject of Research: Persistent C4d deposition on sequential protocol biopsies in ABO-incompatible kidney transplantation

Article Title: Clinical significance of persistent C4d deposition on sequential protocol biopsies in ABO-incompatible kidney transplantation

Article References: Kijima, Y., Ishida, H., Yagisawa, T., Hirai, T., Unagami, K., Shimizu, T., & Takagi, T. (2026). Clinical significance of persistent C4d deposition on sequential protocol biopsies in ABO-incompatible kidney transplantation. Frontiers in Nephrology, 6, Article 1940137. https://doi.org/10.3389/fneph.2026.1940137

Image Credits: AI Generated

DOI: 10.3389/fneph.2026.1940137

Keywords: ABO-incompatible kidney transplantation, C4d, accommodation, antibody-mediated rejection, protocol biopsy, microvascular inflammation, Banff classification, donor-specific antibodies, complement, graft survival, kidney allograft, transplant immunology

The source of the ambiguity lies in the peculiar architecture of the CFH gene itself. From a single genetic locus, cells produce two distinct protein products through alternative splicing. The predominant product is full-length complement factor H, usually abbreviated FH, a large glycoprotein built from twenty complement control protein domains that circulates in plasma and patrols host surfaces, distinguishing self from threat and restraining the alternative pathway of complement activation. The second product is factor H–like 1, or FHL-1, a much smaller splice isoform that consists only of the first seven of those twenty domains, followed by a short, unique C-terminal tail generated by the splicing event. FHL-1 retains the core complement regulatory activities of its larger sibling, including its cofactor function for factor I and its ability to regulate C3b deposition, but it lacks the C-terminal host-recognition domains that allow full-length FH to anchor itself to cell surfaces. In structural and functional terms, these are not interchangeable molecules; they are two tools with overlapping but clearly distinct jobs.

What makes FHL-1 far more than a molecular footnote is where it ends up in the body. It is abundantly expressed in several tissues, and tumour cells themselves, including lung and pancreatic cancer cells, have been shown to produce it, contributing to local complement regulation within the tumour microenvironment. Crucially, FHL-1 exhibits enhanced tissue retention through interactions with the extracellular matrix, the dense protein scaffold that surrounds and structures solid tumours. Because it is smaller than full-length FH and is not glycosylated, FHL-1 can diffuse into and penetrate tightly packed extracellular matrices in a way that the bulky, sugar-decorated full-length protein cannot. Clark points to previous work in the eye, where FHL-1 was identified as the predominant complement regulator in Bruch’s membrane, a densely cross-linked extracellular layer, as evidence of this penetration phenomenon in human tissues. In glioblastoma, meanwhile, researchers have observed increases specifically in FHL-1 expression and secretion, with the hypothesis that the small isoform’s diffusibility allows it to infiltrate the tumour’s matrix-rich architecture.

Against this biological backdrop, the technical critique of the recent pan-cancer analysis becomes easy to understand. The original study by Zheng and colleagues, published in BMC Cancer in 2025, quantified CFH transcription using quantitative reverse-transcription PCR with primers targeting the N-terminal region of the gene. Those primers bind to exons that are shared by both the FH and FHL-1 transcripts. The signal they produce therefore reflects the combined transcription of both isoforms, not full-length factor H alone. The same problem afflicts the functional experiments: the short hairpin RNA constructs used to knock down CFH in pancreatic cancer cells target shared N-terminal sequences, so they would be expected to suppress both FH and FHL-1 simultaneously. The proliferation and migration defects observed after knockdown, in other words, cannot be attributed to either isoform individually. The transcriptional, prognostic, and functional associations reported in the study represent an aggregate FH-plus-FHL-1 signal, without any isoform-specific resolution.

Why should this matter to anyone outside the complement field? The answer lies in how biomarkers are built and validated. Clinical biomarker development depends on clear molecular definition and reproducibility across platforms, assays, and patient cohorts. If FH and FHL-1 are differentially expressed across tumour types, disease stages, or microenvironmental contexts, then an assay that cannot tell them apart will yield signals that are biologically heterogeneous, mixing together two molecules that may behave very differently in different patients. A correlation that holds for the blended signal might be driven almost entirely by one isoform in one cancer and by the other isoform in a different cancer, or it might shift as a tumour progresses and remodels its extracellular matrix. Without isoform resolution, the underlying biology remains invisible behind a single composite number.

The stakes rise further when the two isoforms are considered as potential drivers of tumour biology rather than passive correlates. Because FHL-1 preferentially localizes within the extracellular matrix, it may disproportionately influence local complement activity and immune cell behaviour inside solid tumours, precisely where the battle between tumour cells and immune effectors is fought. Complement is increasingly recognized as a modulator of the tumour microenvironment, shaping inflammation, immune suppression, and the response to immunotherapy. Consequently, correlations reported between aggregate CFH expression and immune infiltration, prognosis, or therapeutic responsiveness may, in some cancers, be driven largely by FHL-1 rather than by full-length FH. If that is the case, the mechanistic story inferred from the data, and the therapeutic strategies built upon it, could be pointed in the wrong direction.

The implications extend directly into the clinic. When CFH transcription is proposed as a diagnostic or prognostic biomarker, or as a marker to guide immunotherapeutic stratification, isoform-specific differences could affect the sensitivity, specificity, and predictive value of FH-based assays. They could also complicate the interpretation of measurements taken from different compartments, since circulating blood levels and tissue-derived levels may reflect different balances of the two proteins. A blood test capturing mostly circulating full-length FH and a tissue assay dominated by matrix-retained FHL-1 could give contradictory answers about the same patient, and clinicians would have no way of knowing which molecule they were actually tracking. In an era when biomarker-driven trials can succeed or fail on the precision of patient selection, such ambiguity is not a trivial technicality.

Importantly, Clark is careful to frame the commentary as a constructive refinement rather than a demolition. He emphasizes that the observation does not detract from the significance or rigour of the original pan-cancer analysis, which he describes as comprehensive and high-quality, integrating transcriptomic data from large public datasets with immune infiltration analyses and in vitro functional validation. That study, he writes, provides a strong foundation for future biomarker-oriented investigations into complement regulation in cancer. The critique is about the next step: studies aimed at clinical translation would benefit from incorporating isoform-resolved approaches before CFH-based signatures are locked into diagnostic pipelines. The tools to do so already exist, including splice-junction–specific quantitative PCR that can distinguish the unique FHL-1 tail from shared exons, long-read RNA sequencing capable of resolving full-length transcript structures, and proteomic methods able to separate the two proteins by mass and by their distinctive C-terminal peptides.

For the broader cancer research community, the episode is a reminder of a principle that applies well beyond complement genetics. Pan-cancer analyses, for all their statistical power, are only as specific as the molecular probes on which they rest, and genes that produce multiple protein products through alternative splicing are a persistent blind spot. The CFH locus is far from unique in this respect, and as transcriptomic biomarkers move from discovery papers toward clinical deployment, the demand for isoform-aware assay design will only grow. Clark’s suggestion is straightforward: refine the measurement, and the clinical utility of FH-based biomarkers may sharpen accordingly, clarifying at the same time how complement regulatory pathways can genuinely be leveraged for cancer diagnosis, prognosis, and therapeutic stratification. The difference between a promising correlation and a deployable diagnostic, it turns out, may hinge on seven protein domains and a short, unique tail.

Subject of Research: Isoform-specific interpretation of CFH gene expression as a pan-cancer biomarker

Article Title: Diagnostic interpretation of CFH expression in pan-cancer analyses: the importance of factor H–like 1 isoform resolution

Article References: Clark, S. J. (2026). Diagnostic interpretation of CFH expression in pan-cancer analyses: the importance of factor H–like 1 isoform resolution. BMC Cancer, 26(1), Article 1214. https://doi.org/10.1186/s12885-026-17134-4

Image Credits: AI Generated

DOI: 10.1186/s12885-026-17134-4

Keywords: CFH, complement factor H, FHL-1, biomarkers, pan-cancer analysis, alternative splicing, tumour microenvironment, complement system, extracellular matrix, prognosis, immunotherapy, qRT-PCR

Weaning is a physiological crucible for goat kids. Abrupt separation from the dam, a sudden shift from milk to solid feed, and an immature rumen converge to create a window of heightened susceptibility to gastrointestinal and respiratory disease. Pre-weaning mortality remains a persistent problem in goat production systems worldwide, and producers have long sought alternatives to prophylactic antibiotics, whose use is increasingly restricted on animal welfare and antimicrobial resistance grounds. Astragalus membranaceus, known in Chinese pharmacopoeia as huangqi, has been used for centuries as an immunomodulatory tonic, and a substantial body of modern research attributes much of its bioactivity to polysaccharides that can influence dendritic cells, macrophages, and B lymphocyte function. What has been missing, however, is a rigorous, molecularly informed assessment of how the herb affects the peripheral immune system of young ruminants specifically.

The research team addressed that gap with a controlled feeding trial involving thirty-six black Xiangdong goat kids, all weaned at postnatal day 42 and weighing on average about 5.3 kilograms. The animals were randomly divided into two groups: a control group of sixteen kids receiving only a basal diet, and a treatment group of twenty kids receiving the basal diet supplemented with ten grams per day of ultrafine-grained Astragalus membranaceus powder, abbreviated UGAM. After an eight-day adaptation period, the supplementation phase ran from postnatal day 43 through day 78, giving the treatment roughly five full weeks of exposure. The choice of ultrafine grinding was deliberate. By reducing particle size dramatically, ultrafine processing increases the surface area available for digestion and absorption, potentially liberating more of the herb’s active polysaccharides and other constituents than conventional coarse powders would allow.

On day 78, the researchers drew blood from every animal and subjected the samples to a battery of immunological assays. They quantified seven complement proteins spanning the classical and regulatory arms of the cascade, C1q, C1r, C1s, C3, C4, C4bp, and Factor H, together with the three major immunoglobulin classes, IgA, IgG, and IgM, and a panel of six inflammatory cytokines including IL-1α, IL-1β, IL-6, IL-10, TNF-α, and IFN-γ. Complete peripheral blood cell profiles rounded out the picture. In a randomly selected subset of eleven control animals and sixteen treated animals, the team also measured hepatic expression of complement-related genes using reverse transcription quantitative PCR, capitalizing on the fact that the liver is the principal site of complement protein synthesis and an increasingly recognized hub of systemic innate immunity.

The results were strikingly specific. Serum concentrations of C4bp, a glycoprotein that acts as a major negative regulator of the classical and lectin complement pathways by accelerating the decay of C3 and C5 convertases and serving as a cofactor for Factor I-mediated cleavage of C4b, rose significantly in the treated animals. Crucially, this increase was mirrored at the transcript level: hepatic C4bp mRNA expression was also significantly elevated, with the serum protein and liver gene expression changes both reaching statistical significance at p less than 0.001. This concordance between circulating protein and hepatic messenger RNA suggests that the herb acts, at least in part, by transcriptionally upregulating complement regulatory machinery in the liver rather than merely altering protein clearance or distribution. Alongside the C4bp signal, the treated kids showed significantly higher circulating IgM, the phylogenetically oldest and first-response antibody class, produced early in immune responses by naive B cells.

Equally informative was what did not change. Levels of IgA and IgG, the other two immunoglobulin classes measured, remained statistically indistinguishable between the groups, as did all six inflammatory cytokines. This absence of cytokine elevation is arguably as important as the increases themselves. Many immunostimulatory feed additives work, when they work, by provoking a mild inflammatory response, which carries metabolic costs and risks of tissue damage if sustained. The UGAM-treated animals instead exhibited a pattern consistent with homeostatic tuning: an expanded complement regulatory capacity and a bolstered first-line humoral defense, achieved without activating pro-inflammatory or even broadly anti-inflammatory cytokine programs. The researchers interpreted this as evidence of engagement of the body’s homeostatic complement regulatory system rather than blunt immune activation.

To test whether the observed changes were genuinely linked to the treatment rather than artifacts of multiple comparisons, the team employed a multi-parameter statistical framework. In that analysis, UGAM supplementation emerged as independently and positively associated with C4bp levels, with a partial correlation coefficient of 0.74 and a p-value below 0.001, a robust effect size for a nutritional intervention in a livestock trial. Furthermore, a Mantel test comparing the overall correlation structures of the complement system and the immunoglobulin panel revealed significant concordance between the two modules, with a Mantel statistic of 0.36 and p equal to 0.001. This suggests that the complement and antibody arms of humoral immunity moved together in response to the intervention, consistent with the well-documented crosstalk between complement activation products and B cell responses, in which complement receptor engagement shapes antibody quality and magnitude.

The study builds on a growing literature exploring Astragalus preparations across livestock species. Previous work has documented improved growth performance, serum immunity, and antioxidant status in Tibetan sheep and finishing lambs supplemented with Astragalus root, enhanced intestinal health and gut microbiota profiles in broilers fed Astragalus-derived polysaccharides, and protective effects on mucosal immunity in immunosuppressed poultry. An earlier companion study by some of the same authors showed that ultra-ground Astragalus supplementation altered ileal microbiome composition and mucosal immune profiles in weaned goats, and the new work extends that picture to the systemic, liver-centered complement axis. Notably, several prior studies linked Astragalus polysaccharides to effects on NF-κB signaling and trained immunity pathways, providing plausible mechanistic scaffolding for the observed hepatic transcriptional changes, though the present study did not directly assay these signaling pathways.

The authors are appropriately measured about the limits of their evidence. Complement activity itself, as opposed to component concentrations, was not measured, and neither were plasma cell responses, downstream signaling events, or formal safety parameters, leaving the precise mechanisms behind the observed C4bp and IgM elevations hypothetical and requiring validation in future experiments. The treatment group was also larger than the control group, and hepatic gene expression was assessed in a subset rather than the full cohort. Nonetheless, the internal consistency of the findings, spanning protein, transcript, and multivariate correlation analyses, lends the central conclusion considerable weight. The trial was funded by China’s National Key Research and Development Program and the Natural Science Foundation of Guangxi, and the analysis code has been made publicly available on GitHub, an increasingly welcome transparency measure in animal science.

If replicated and extended, the implications extend beyond goat husbandry. The complement system sits at the intersection of innate and adaptive immunity, and pharmacological or nutritional modulation of its regulatory arm, particularly C4bp, is an active frontier in human medicine, with complement-targeting therapeutics advancing for conditions ranging from nephropathy to autoimmune disease. Demonstrating that a simple dietary herb powder can shift complement regulatory tone in a large animal model, without inflammatory side effects, offers a conceptual bridge between traditional herbal medicine and modern molecular immunology. For producers of black Xiangdong goats, a breed valued in subtropical China, the prospect of a ten-gram daily supplement that meaningfully supports humoral immunity through the perilous post-weaning weeks is an attractive one. The next step, the researchers indicate, will be to confirm the mechanisms, verify safety over longer durations, and determine whether the immunological gains translate into measurable improvements in disease resistance and survival under field conditions.

Subject of Research: Effects of oral ultrafine-grained Astragalus membranaceus supplementation on complement regulator C4bp and immunoglobulin responses in weaned goats

Article Title: Oral administration of ultrafine-grained Astragalus membranaceus enhances peripheral immunity in weaned black Xiangdong goats by upregulating the complement regulator C4bp and immunoglobulin responses

Article References: Liao, J., Sun, J., Gebeyew, K., Khan, N. A., & Liu, Y. (2026). Oral administration of ultrafine-grained Astragalus membranaceus enhances peripheral immunity in weaned black Xiangdong goats by upregulating the complement regulator C4bp and immunoglobulin responses. Molecular Biology Reports, 53(1), Article 1680. https://doi.org/10.1007/s11033-026-12883-8

Image Credits: AI Generated

DOI: 10.1007/s11033-026-12883-8

Keywords: Astragalus membranaceus, complement system, C4bp, immunoglobulins, IgM, weaned goats, ultrafine grinding, hepatic gene expression, innate immunity, humoral immunity, livestock nutrition, Xiangdong goats

The study, published in Virology Journal by Ying Li of Zhengzhou Railway Vocational and Technical College and colleagues at Zhengzhou University and Henan Children’s Hospital, focused on children of Han Chinese ethnicity who were infected with Coxsackievirus A6, an enterovirus that has increasingly displaced enterovirus 71 as the dominant cause of hand, foot, and mouth disease outbreaks in many regions. The research team enrolled 189 children from Henan Children’s Hospital, dividing them into 94 severe cases and 95 mild cases, and then asked whether specific single nucleotide polymorphisms, or SNPs, in complement-related genes were more common among the severely ill children than among those with milder disease.

The complement system is a cascade of plasma proteins that acts as one of the body’s first lines of defense against pathogens. When activated, complement proteins such as C3 and C5 mark microbes for destruction, recruit inflammatory cells to sites of infection, and in some circumstances directly punch holes in viral envelopes or infected cell membranes. Because the complement cascade sits at the interface between pathogen recognition and inflammatory damage, it represents a biologically plausible target for genetic studies of infection severity: too little complement activity might impair viral clearance, while too much might fuel the excessive inflammation that characterizes severe cases. The central complement protein C3, the terminal component C5, and the complement regulatory protein factor H, encoded by the CFH gene, each play distinct roles in this delicate balance, and common genetic variants in these genes have previously been linked to susceptibility to other infectious and inflammatory diseases.

To test whether such variants matter in Coxsackievirus A6 infection, the researchers extracted genomic DNA from peripheral blood leukocytes using a modified phenol-chloroform method and performed SNP genotyping by polymerase chain reaction followed by restriction fragment length polymorphism analysis, a classical technique in which PCR-amplified DNA fragments are digested with restriction enzymes whose cutting patterns differ depending on the nucleotide present at a given position. This approach allowed the team to determine each child’s genotype at candidate SNPs in the C5, C3, and CFH genes and to compare genotype frequencies between severe and mild cases using both crude and multivariable logistic regression models adjusted for age group and sex.

The results revealed several nominal associations. Children carrying the GA genotype at rs3761847 in the C5 gene had roughly two and a half times the odds of severe disease compared with those carrying the GG genotype, with an adjusted odds ratio of 2.523 and a 95 percent confidence interval spanning 1.036 to 6.143. At rs2250656 in the C3 gene, the TC genotype was associated with an adjusted odds ratio of 1.982, with a confidence interval of 1.061 to 3.704, relative to the TT genotype. The strongest signals emerged at rs1065489 in the CFH gene, where the TT genotype conferred an adjusted odds ratio of 3.125, with a confidence interval of 1.249 to 7.818, and the GT genotype an adjusted odds ratio of 2.499, with a confidence interval of 1.118 to 5.588, both relative to the GG genotype. Taken at face value, these findings suggest that children carrying particular alleles at these three loci face a substantially elevated risk of progressing to severe hand, foot, and mouth disease once infected with Coxsackievirus A6.

However, the authors are careful to emphasize a critical statistical caveat. When the analysis was corrected for multiple testing using the Bonferroni method, a conservative procedure that adjusts the significance threshold to account for the number of SNPs examined, none of these associations remained statistically significant. This is a common and important pattern in candidate-gene association studies, which typically examine a modest number of preselected variants in a limited number of participants. Nominal signals that vanish after correction may reflect true effects that the study lacked the statistical power to confirm, or they may simply be chance findings that arise whenever many genetic variants are tested simultaneously in a finite sample. Distinguishing between these possibilities requires replication in independent cohorts, which is precisely what the authors call for.

Beyond the individual SNP analyses, the team also evaluated whether a combined model incorporating multiple SNPs could discriminate severe from mild cases. The combined model showed limited discriminatory performance, achieving an apparent area under the receiver operating characteristic curve of 0.653, which declined to 0.631 after bootstrap-based optimism correction. An AUC of 0.5 indicates discrimination no better than chance, while 1.0 indicates perfect discrimination, so a corrected value of 0.631 suggests that complement-related variants alone, at least in this cohort, provide only modest predictive information about disease severity. This finding underscores a broader lesson in genetic epidemiology: complex clinical outcomes such as infection severity are rarely determined by a handful of variants in a single pathway, and even biologically plausible genetic associations often translate into weak predictive models when considered in isolation.

The study also reported exploratory differences in selected laboratory parameters across genotype groups, hinting that complement variants might correlate with measurable differences in the host response to infection, although the authors frame these observations as preliminary. Such genotype-phenotype correlations, if confirmed, could eventually help explain the biological mechanism linking specific variants to clinical outcomes, for example by altering complement protein levels, activation efficiency, or regulation of the inflammatory response during enterovirus infection.

The clinical context of this work is significant. Coxsackievirus A6 has emerged as a major cause of hand, foot, and mouth disease in China and elsewhere, and unlike enterovirus 71, for which vaccines have been developed and deployed, CVA6 has no licensed vaccine. Surveillance data have shown shifting patterns of enterovirus dominance, with CVA6 outbreaks producing atypical and sometimes severe presentations, including widespread eczema coxsackium in children with atopic dermatitis and occasional neurological involvement. Understanding the host-side determinants of severity therefore has practical value: if genetic risk factors could be reliably identified and validated, they might eventually inform risk stratification in clinical settings, helping clinicians identify which children warrant closer monitoring during outbreaks.

The study was conducted in accordance with the Declaration of Helsinki and approved by the Life Sciences Institutional Review Board of Zhengzhou University, with written informed consent obtained from the parents or legal guardians of all participants. Funded by the National Natural Science Foundation of China and several provincial and postdoctoral programs, the work exemplifies the growing effort to move beyond purely virological explanations of disease severity and toward an integrated view in which viral factors, host genetics, and immune status jointly shape clinical outcomes. For now, the message of this study is one of cautious hypothesis generation: complement-related variants in C5, C3, and CFH merit further investigation as potential modifiers of Coxsackievirus A6 disease severity, but larger, independent, and ideally multi-center cohorts will be needed before these genetic signals can be considered established or translated into clinical tools. In a field where most children recover uneventfully and only a minority deteriorate, even modest advances in understanding host susceptibility could ultimately sharpen the clinical response to one of the world’s most burdensome pediatric viral diseases.

Subject of Research: Association between complement-related gene polymorphisms and severity of Coxsackievirus A6-induced hand, foot, and mouth disease in Chinese Han children

Article Title: Complement-related gene polymorphisms and severity of Coxsackievirus A6-induced hand, foot, and mouth disease in chinese han children: a candidate-gene association study

Article References: Li, Y., Li, Z., Duan, G., Chen, S., Zhang, Y., Wang, F., Dai, B., & Jin, Y. (2026). Complement-related gene polymorphisms and severity of Coxsackievirus A6-induced hand, foot, and mouth disease in chinese han children: a candidate-gene association study. Virology Journal. https://doi.org/10.1186/s12985-026-03282-3

Image Credits: AI Generated

DOI: 10.1186/s12985-026-03282-3

Keywords: hand, foot, and mouth disease, Coxsackievirus A6, complement system, C5, C3, CFH, single nucleotide polymorphisms, genetic association study, disease severity, enterovirus, pediatric infectious disease, innate immunity

The biology at the heart of the study begins at the neuromuscular junction, the microscopic relay where motor neurons hand their signals to muscle fibers. In the most common form of myasthenia gravis, autoantibodies bind the acetylcholine receptor clustered on the muscle side of this synapse. Those antibodies do more than simply block the receptor; many of them recruit the complement system, an ancient arm of immune defense designed to punch holes in the membranes of invading microbes. When complement is triggered at the synapse, it assembles the membrane attack complex, a pore-forming structure that tears into the postsynaptic membrane. The result is destruction of the synaptic folds, loss of acetylcholine receptors, inflammatory infiltration of macrophages into the endplate region, and ultimately a failure of neuromuscular transmission that patients experience as drooping eyelids, double vision, and life-threatening weakness of the muscles that control breathing and swallowing.

Complement activation follows a strictly ordered cascade, and C3 sits at its pivotal center. All major activation pathways converge on this protein, which, once cleaved, seeds opsonization of target tissue, amplifies the response through amplification loops, and drives the terminal assembly of the membrane attack complex. This convergence point has long made C3 an attractive therapeutic target, and drugs that inhibit it are already reshaping the treatment landscape of several complement-mediated disorders. What the new study adds is a direct test, in a rigorous animal model, of whether near-total elimination of circulating C3, achieved not with a blocking antibody but by silencing the gene that produces the protein in the liver, can prevent the structural and functional damage of myasthenia gravis during its acute phase.

The experimental approach relied on small interfering RNA, short synthetic RNA molecules that hijack the cell’s own RNA-induced silencing complex to degrade a specific messenger RNA before it can be translated into protein. To make sure the siRNA reached its destination, the researchers equipped it with a triantennary N-acetylgalactosamine ligand, a chemical handle that binds with high affinity to the asialoglycoprotein receptor abundantly displayed on hepatocytes. This GalNAc-targeting technology, which has already transformed the delivery of other liver-directed RNA therapies, allowed the compound to be administered by simple subcutaneous injection rather than intravenous infusion. Female Lewis rats received the C3-siRNA at different dosages before the researchers induced disease by passive transfer, injecting a monoclonal antibody directed against the acetylcholine receptor, a model known as passive transfer myasthenia gravis that reproduces the acute complement-mediated attack on the synapse without requiring the animals to mount their own autoimmune response.

The degree of target engagement was remarkable. Two administrations of the C3-siRNA at 30 milligrams per kilogram, spaced one week apart, reduced plasma C3 levels by more than 98 percent, pushing them below the detection limit of the assay. Against this near-total depletion of the central complement component, the researchers then challenged the animals with the pathogenic anti-receptor antibody and tracked the consequences with an unusually comprehensive battery of readouts: clinical scoring of weakness, direct measurements of muscle strength, electromyographic assessment of transmission failure at the junction, quantification of total and functional acetylcholine receptor levels in muscle, histological analysis of macrophage infiltration and sectional necrosis in the motor endplate region, and immunostaining for complement activation products deposited at the synapse.

The protective effect was evident across essentially every parameter measured. Treated animals showed significantly reduced deposition of the membrane attack complex at the neuromuscular junction, indicating that the terminal complement attack had been blunted. The characteristic tissue damage of the disease was correspondingly diminished: sectional necrosis within the endplate region was reduced, and the influx of macrophages that normally follows complement-mediated injury was attenuated. Skeletal muscle C3 messenger RNA, which is upregulated locally during the disease process, rose less in the treated animals. Importantly, the therapy partially preserved functional acetylcholine receptor levels, meaning that the receptors remaining at the synapse were better able to do their job of transmitting neuronal signals to the muscle. The structural preservation translated into function: muscle strength assessments and electromyography showed that the development of muscle weakness was effectively attenuated in the treated rats compared with controls.

Perhaps the most scientifically provocative observation came from what the treatment did not achieve. Despite the near-total elimination of C3 from the plasma, low levels of C3 activation products and membrane attack complex were still detectable specifically at the neuromuscular junction. This residual deposition is more than a technical footnote. It demonstrates that even a vanishingly small amount of circulating C3 is sufficient to sustain some degree of complement activation at the inflamed synapse, where local amplification mechanisms and the intense concentration of activating antibodies can make the most of scarce substrate. The authors interpret this as evidence of the powerful pathogenic potency of C3 in acetylcholine receptor-positive myasthenia gravis: the protein is so effective a driver of tissue injury that even trace quantities can leave a molecular fingerprint of damage at the junction.

That observation carries practical implications for how complement-targeted therapies might be deployed in patients. If near-complete suppression of plasma C3 leaves residual terminal pathway activity at the neuromuscular junction, then the therapeutic goal in myasthenia gravis may need to be either maximally deep C3 suppression, combination approaches that pair hepatic silencing with additional inhibition at the tissue level, or careful biomarker monitoring of complement deposition at the synapse itself rather than relying solely on systemic measures. At the same time, the study shows that the degree of protection achieved with hepatic silencing alone was already substantial, preserving receptor function and blunting weakness in the acute disease phase, which supports the idea that C3 silencing could serve as an adjunctive therapy layered onto existing immunosuppressive regimens rather than replacing them outright.

The work also illustrates how the tools of molecular medicine are being repurposed for organ-specific immunology. Rather than designing a protein drug to neutralize C3 in the bloodstream, the team used a GalNAc-conjugated siRNA to instruct the liver itself to stop making the protein, achieving durable, deep, and convenient subcutaneously delivered target reduction. This strategy builds on the broader success of RNA interference therapeutics in hepatic targets and suggests that complement proteins synthesized primarily by the liver are well suited to this modality. For a disease like myasthenia gravis, where chronic immunosuppression carries significant long-term burdens and where existing complement inhibitors require frequent intravenous administration, a long-acting subcutaneous gene-silencing approach could meaningfully change the treatment calculus, although the authors are careful to frame the current results as preclinical support for a potential adjunctive strategy rather than a validated therapy.

As with any animal study, the path from Lewis rats to patients runs through the usual gauntlet of safety, dosing, and clinical trial design, and the passive transfer model captures the acute effector phase of the disease rather than the full chronic autoimmune process that unfolds in patients. Nevertheless, the study delivers a clear and technically rigorous message: C3 is a dominant and remarkably potent driver of the complement-mediated destruction of the neuromuscular junction in antibody-positive myasthenia gravis, silencing its hepatic production protects receptor levels, synaptic architecture, and muscle function, and even the faint residual complement activity that survives near-total depletion underscores how aggressively this pathway must be restrained. For a disease in which the immune system’s own microbial-killing machinery turns against the synapse, teaching the liver to hold that machinery back may prove to be one of the more consequential therapeutic ideas to emerge from complement research in recent years.

Subject of Research: Complement C3 gene silencing as a therapy for complement-mediated neuromuscular junction damage in myasthenia gravis

Article Title: C3 complement silencing prevents acetylcholine receptor loss and reduces complement activation in the rat passive transfer myasthenia gravis model

Article References: Schöttler, A. K., Mané-Damas, M., Arets, B., Peng, S., Molenaar, P. C., De Baets, M. H., Claessen, S. M. H., Barbour, T., Richardson, E., Eyerman, D. J., Scheibler, L., Losen, M., & Martinez-Martinez, P. (2026). C3 complement silencing prevents acetylcholine receptor loss and reduces complement activation in the rat passive transfer myasthenia gravis model. Journal of Translational Medicine. https://doi.org/10.1186/s12967-026-08832-5

Image Credits: AI Generated

DOI: 10.1186/s12967-026-08832-5

Keywords: myasthenia gravis, complement C3, neuromuscular junction, small interfering RNA, GalNAc delivery, membrane attack complex, acetylcholine receptor, passive transfer model, complement inhibition, gene silencing, autoimmune disease, Lewis rats

The target in question is C4d, a small fragment of the complement system, the branch of innate immunity that normally helps antibodies destroy microbes and damaged cells. When a therapeutic antibody binds to its antigen on a tumor cell surface, it can trigger the classical complement cascade. Complement component C4 is cleaved, and the active product C4b forms a covalent bond with nearby molecules on the cell membrane. That covalent attachment is crucial, because it means the fragment stays glued to the cell even after the cascade fizzles out. C4b is then progressively inactivated and cleaved by complement regulators, ultimately leaving C4d as the terminal degradation product, still anchored in place.

Here lies the central insight of the study. Tumor cells that survive an antibody assault do so largely because they are protected by complement inhibitors, both membrane-bound proteins such as CD55 and CD59 and soluble regulators circulating in the blood. These inhibitors shut down the cascade before the membrane attack complex, the pore-forming assembly that punches lethal holes in cell membranes, can fully form. But the shutdown process itself leaves C4d behind, covalently deposited on the membrane. In other words, every cell that has been challenged by a complement-activating antibody and lived to tell the tale carries a permanent footprint of that encounter. Cells that were never touched by the first antibody carry no such mark.

This makes C4d a molecular signature of prior antibody exposure, and, more provocatively, a target for a follow-up attack. The research team engineered a candidate anti-C4d antibody as a chimeric human-rabbit construct, a design that combines the specificity of the rabbit-derived binding region with a human antibody framework intended to reduce immunogenicity. Critically, they introduced amino acid substitutions that enhance oligomerization, meaning the antibody molecules cluster more readily once bound to C4d on the cell surface. That clustering matters because complement activation depends on the density of antibody Fc regions; a tightly packed array of Fc domains recruits and assembles the C1 complex far more efficiently than scattered individual antibodies, and therefore ignites a stronger classical pathway response.

To test the concept, the researchers pretreated human lymphoma and breast cancer cells with standard immunotherapeutics and then challenged the surviving cells with the anti-C4d antibody in the presence of normal human serum, which supplies the full repertoire of complement proteins. The results were striking. Applying the anti-C4d antibody significantly increased the killing of lymphoma cells that had previously been treated with the anti-CD20 antibodies rituximab or obinutuzumab, or with the anti-CD38 antibody daratumumab, compared with simply re-treating the cells with the same antibody a second time. The resistant cells, marked by their C4d deposits, became preferential targets of a fresh complement attack.

The effect extended to the hardest cases. The team worked with lymphoma sublines that had been selected for resistance to rituximab, models that represent the clinical nightmare of relapse after anti-CD20 therapy. Even in these sublines, the anti-C4d approach boosted complement-mediated cytotoxicity, suggesting that resistance to the primary antibody does not necessarily abolish the footprint it leaves, nor the ability of a second antibody to exploit it. The strategy also worked in a setting where the first antibody barely activates complement at all: a human breast cancer cell line treated with trastuzumab, the anti-HER2 therapeutic that by itself induced no measurable complement-dependent cytotoxicity in these experiments. Even that weak, sublethal complement activation was enough to deposit C4d, and the anti-C4d antibody converted those sparse deposits into a robust secondary wave of killing.

From a mechanistic standpoint, the approach can be understood as a two-stage amplifier. The first antibody, whether it is rituximab, obinutuzumab, daratumumab or trastuzumab, performs a dual function: it kills some cells directly through complement and immune effector mechanisms, and it tags the survivors with C4d. The second antibody then reads that tag and recruits the complement system again, this time against cells that have already demonstrated they can withstand the first round. Because C4d is covalently bound and resistant to further enzymatic removal, the tag persists on the membrane, giving the second antibody a stable epitope that does not depend on the tumor cell continuing to express the original antigen at high levels, a common escape route in antibody therapy resistance.

The concept also sidesteps several problems that plague conventional second-line strategies. Re-treating patients with the same antibody often fails because antigen expression has dropped or complement regulators have been upregulated, and switching to a different antigen-targeting antibody requires that the new antigen be present and accessible. C4d, by contrast, is deposited as a direct consequence of the first treatment itself, so its presence is essentially guaranteed on cells that experienced complement activation. The approach is therefore not tied to any particular tumor type or antigen; in principle, any complement-activating first-line antibody creates the substrate for the second-line anti-C4d antibody. The authors describe such antibodies as immunotherapeutic amplifiers, capable of converting limited complement activation induced by a primary antibody into a powerful secondary wave of complement-mediated killing.

There are important caveats. This is an in vitro study, conducted with cell lines and normal human serum rather than in patients, and the transition from cell culture to the clinic involves formidable challenges, including the pharmacokinetics of a second antibody, the accessibility of C4d deposits within solid tumors, and the risk of off-target effects on healthy tissues that might carry complement deposits from inflammation. The team also has commercial interests in the technology: Anna Blom and Marcin Okrój are named inventors on a European patent covering antibodies specific for C4d, and a further patent application covers the use of anti-C4d antibodies as second-line immunotherapeutics for patients resistant to first-line therapy. Budka and Okrój receive royalties from a company that commercialized the earlier invention. These disclosures do not diminish the scientific interest of the work, but they signal that the researchers see a clear path toward translation.

Still, the conceptual shift is what makes the study noteworthy. For decades, complement has been viewed mainly as an effector arm that therapeutic antibodies recruit, and resistance has been viewed as a property of the tumor to be overcome with new targets or new drugs. This work reframes the complement fragments left on surviving cells as an opportunity rather than a byproduct, turning the debris of a failed attack into the aiming point for the next one. If the strategy can be validated in animal models and eventually in clinical trials, patients who relapse after rituximab, daratumumab or trastuzumab might one day receive a follow-up antibody that does not need to find a new molecular target at all, because the first treatment has already marked the enemy.

Subject of Research: Targeting the complement C4d fragment to overcome resistance to antibody-based cancer immunotherapy

Article Title: Targeting C4d to overcome resistance to antibody-based immunotherapy: an in vitro study

Article References: Budka, D., Stasiłojć, G., Stasiłojć, M., Kusowska, A., Bieńkowski, M., Bobrowicz, M., Blom, A. M., Winiarska, M., & Okrój, M. (2026). Targeting C4d to overcome resistance to antibody-based immunotherapy: an in vitro study. Cancer Immunology, Immunotherapy. https://doi.org/10.1007/s00262-026-04567-w

Image Credits: AI Generated

DOI: 10.1007/s00262-026-04567-w

Keywords: C4d, complement system, monoclonal antibodies, immunotherapy resistance, rituximab, obinutuzumab, daratumumab, trastuzumab, lymphoma, breast cancer, complement-dependent cytotoxicity, cancer immunotherapy