It also addresses a practical problem for immunologists: designing reliable experiments and making sense of the resulting data can be technically challenging and conceptually opaque. The authors present the review as a guide for researchers beginning to incorporate metabolomics into immunology. It outlines key methodological approaches and considers common challenges alongside potential solutions, with the aim of lowering the barrier to entry for laboratories that may otherwise regard the field as inaccessible.

The guidance is intended to help immunologists design initial experiments, interpret metabolomic data produced by others and confidently incorporate metabolic measurements into their research. A central part of the article is a step-by-step roadmap for interpreting nutrient-tracing data. The review explains how readers can work through complex isotopologue datasets and draw meaningful conclusions from them.

The review’s broader message is that the expanding recognition of metabolism in immune biology is creating demand for analytical tools capable of capturing metabolic states across different conditions. Metabolomics offers one such tool because it profiles the metabolites that reflect cells’ energy use and biosynthetic activity.

Subject of Research: Practical metabolomics methods for studying immune-cell metabolism and interpreting nutrient-tracing data.

Article Title: Navigating metabolomics in the era of immunometabolism

Article References: Slattery, K., Avizonis, D. Z., O’Connor, G. M., & Gardiner, C. M. (2026). Navigating metabolomics in the era of immunometabolism. Journal of Translational Medicine. https://doi.org/10.1186/s12967-026-08998-y

Image Credits: AI Generated

DOI: 10.1186/s12967-026-08998-y

Keywords: metabolomics, immunometabolism, immune cells, metabolic pathways, bioenergetics, nutrient tracing, isotopologues, immunology, translational medicine, Navigating, scientific research

ANCA-associated glomerulonephritis is one of the most serious manifestations of ANCA-associated vasculitis, a group of autoimmune conditions in which the body produces antibodies against proteins normally found in neutrophils, the rapidly responding white blood cells that form the first line of defense against infection. When these autoantibodies bind neutrophils, they can push the cells into a destructive state in which they attack the small blood vessels of the kidney’s filtering units, the glomeruli. The resulting inflammation destroys kidney tissue and can progress rapidly to organ failure. Although treatment options have improved in recent years, current therapies rely heavily on broad immunosuppression, which carries risks ranging from serious side effects of prolonged use to outright treatment failure.

Lead author Masayuki Nishide explains why the kidney makes such a valuable window into the autoimmune process. In ANCA-associated glomerulonephritis, the kidneys are frequently involved, which makes the organ an excellent candidate for studying the initial steps of the autoimmune disease sequence. Yet until now, little was known about the order of events that unfold in the earliest phase of the disease, precisely the stage at which an intervention could prevent the most damage.

To reconstruct that sequence, the researchers compared kidney samples from healthy donors with samples from patients with ANCA-associated glomerulonephritis who had not yet received treatment. Using spatial transcriptomics, a cutting-edge technology that reads out gene activity across a tissue while preserving the physical organization of the cells, they studied the progression of the disease in its native cellular context. This approach matters because autoimmune injury is not just about which cells are present but about where they sit relative to one another, and conventional methods that break tissue apart lose exactly that information.

The comparison produced a striking result. Diseased kidneys showed more cellular damage than normal ones, but the changes went deeper than expected. Senior author Atsushi Kumanogoh notes that the team was surprised to find that even in tissue that appeared normal under standard examination, changes could still be detected at the cellular level. The goal, he says, was to investigate exactly how the disease unfolds in the early stage so that it could be stopped before significant damage is done.

The spatial maps revealed a specific pathogenic architecture. Injured proximal tubular epithelial cells, the kidney cells that line the tubules and perform much of the organ’s reabsorptive work, send out signals that attract immune cells, including neutrophils. The accumulating neutrophils cluster around the damaged epithelial cells, forming a local microenvironment the researchers term a neutrophil–epithelial niche. Within this niche, the two cell populations reinforce each other: the injured epithelial cells recruit and stimulate the neutrophils, and the activated neutrophils drive the spread of inflammation through the surrounding kidney tissue. Excessive neutrophil activation emerged as a key feature of early disease, positioning these cells not as innocent bystanders but as central engines of the injury process.

That insight suggested a specific molecular target. Neutrophil activation in this disease depends on Fcγ receptors, the cell-surface proteins that recognize the tail region of antibodies and translate antibody binding into cellular responses. In ANCA-associated glomerulonephritis, stimulation of Fcγ receptors by the disease autoantibodies is integral to the development of the inflammatory process. The researchers therefore engineered modified antibodies designed to minimize stimulation of these receptors, aiming to dampen neutrophil activation without eliminating the cells altogether.

To test the approach, the team replicated the kidney injury in a mouse model of the disease and treated the animals with the modified antibodies. The results were promising: the engineered antibodies successfully reduced kidney injury in the model. By quieting the Fcγ receptor signals that fuel neutrophil activation, the treatment appears to act on the mechanism that drives the earliest phase of the disease, rather than on downstream inflammation that has already caused tissue destruction.

The findings point to a potential new therapeutic strategy aimed at stopping ANCA-associated glomerulonephritis at its earliest stage, before severe kidney damage develops. Because the approach targets a defined step in the disease mechanism, it could in principle offer patients safer treatments with fewer side effects than the broad immunosuppressive regimens used today. The researchers hope that continued development in this area can translate the mouse-model results into clinical benefit, giving patients new options at the stage of disease where intervention matters most.

The study, titled Epitope-diverse autoantibodies induce neutrophil–epithelial niches driving kidney injury in ANCA-associated glomerulonephritis, involved collaboration with Chugai Pharmaceutical Co., Ltd. Several co-authors are employees of and shareholders in the company, and Atsushi Kumanogoh has received grant support from Chugai Pharmaceutical. The work was conducted at the Immunology Frontier Research Center of the University of Osaka using human tissue samples alongside the experimental mouse studies, and it was published in the Journal of Experimental Medicine with the DOI 10.1084/jem.20260506.

Subject of Research: ANCA-associated glomerulonephritis early disease mechanism and modified antibody treatment

Article Title: Curbing the neutrophil surge: New treatment offers hope for autoimmune diseases

Article References: Curbing the neutrophil surge: New treatment offers hope for autoimmune diseases. Original publication (Bibliographic details unavailable.)

Image Credits: AI Generated

DOI: Not provided

Keywords: ANCA-associated vasculitis, glomerulonephritis, neutrophils, autoimmune disease, spatial transcriptomics, Fcγ receptors, kidney injury, University of Osaka, Journal of Experimental Medicine, modified antibodies, neutrophil–epithelial niche, immunology

LGMD R12 is an autosomal recessive myopathy caused by pathogenic variants in anoctamin-5, a multipass membrane protein that sits in the sarcolemma and sarcoplasmic reticulum of muscle fibers. The protein participates in calcium-activated chloride channel activity, plasma membrane repair, and the maintenance of muscle fiber homeostasis. When both copies of the gene are disabled, patients develop progressive weakness and atrophy of the pelvic and shoulder girdle muscles, though the clinical picture varies widely and serum creatine kinase levels can range from normal to dramatically elevated. No effective therapy currently exists, and the molecular cascade connecting the mutated gene to dying muscle has remained stubbornly obscure. That gap is precisely what the new study set out to close.

The patient at the center of the story arrived at the rheumatology department with nine months of exercise-induced muscle pain and hyperCKemia, creatine kinase levels swinging between 3,079 and 8,386 units per liter against a normal ceiling of 200. He had no rash, normal muscle tone, and full grade V strength, a presentation that easily mimics idiopathic inflammatory myopathy or glycogen storage disease. A right deltoid biopsy showed muscle fiber hypertrophy and necrosis without lymphocytic infiltration, and genetic testing ultimately revealed the culprit: a homozygous duplication in exon 10 of ANO5, designated c.898dupA (p.Ile300fs), a frameshift variant not previously reported in the literature. Both of his parents carried the same mutation in heterozygous form, the classic signature of recessive inheritance. At a two-year follow-up the patient remained able to perform normal daily activities, with creatine kinase hovering near 3,000 to 4,000 units per liter.

The team, working with samples gathered during an earlier study of inflammatory myopathies, sequenced biceps brachii muscle tissue and peripheral blood mononuclear cells from the patient alongside samples from healthy controls. After rigorous quality control, 38,477 muscle cells entered the analysis, 8,994 from the patient and 29,483 from three controls undergoing lipoma surgery, together resolving into fifteen distinct clusters. Cell identity was assigned using canonical marker genes, batch effects were corrected with Harmony, and clusters were visualized through uniform manifold approximation and projection. Consistent with the genetic diagnosis, ANO5 expression was barely detectable at the single-cell RNA level, and the proportion of mature myocytes in the patient was significantly reduced, an early hint that the disease was dismantling the cellular architecture of the muscle from the inside out.

Reclustering the myocytes revealed four subpopulations: muscle progenitor cells, slow-twitch type I fibers, fast-twitch type II fibers, and an intermediate state transitioning from progenitors toward type II fibers. The pattern in the patient was stark. Progenitor cells had multiplied, while type I fibers had all but vanished, and trajectory analysis with Monocle showed the patient’s muscle cells largely frozen in an undifferentiated state. In other words, the regenerative compartment was stocked with raw material that simply could not mature. Immunofluorescence staining of frozen muscle sections confirmed the single-cell story, demonstrating a dramatic loss of both MYH7-positive type I fibers and MYH2-positive type II fibers relative to controls, with laminin staining delineating the shrunken fiber outlines. The contraction-related gene RPL3L was also markedly downregulated, further underscoring the failing contractile machinery.

The metabolic findings may prove just as consequential. Gene ontology and single-cell metabolic pathway analyses, the latter quantifying KEGG-curated pathway activity in each individual cell, showed significant downregulation of glycolytic activity and broader cellular metabolism, spanning nucleotide, energy, carbohydrate, and amino acid pathways. The downregulation was most pronounced in type I fibers, which depend heavily on oxidative phosphorylation, suggesting a maladaptive metabolic shift away from aerobic energy production that could accelerate atrophy. Prior work has shown that ANO5 deficiency impairs myoblast membrane repair through disrupted calcium handling, and the new data connect that biophysical defect to a systemic bioenergetic collapse. Dysregulated energy and biosynthetic processes, the authors argue, likely feed directly into the contractile dysfunction that defines the disease.

Then came the immunological surprise. Although the patient’s biopsy showed no lymphocytic infiltration, the single-cell data told a different story. Within the muscle, B cells had expanded significantly, and gene sets for leukocyte migration and chemotaxis were highly enriched while muscle development pathways withered. Using CellChat, a computational framework that models ligand-receptor signaling between cell types, the researchers mapped heightened immune crosstalk between macrophages and neutrophils, with the LGALS9-CD45/CD44 and ANXA1-FPR1 pathways prominently activated, alongside IL1β-IL1R2 and several chemokine axes. The peripheral blood told a parallel tale: among 8,161 patient PBMCs compared with 25,685 control cells across fourteen cell types, B cells had again expanded, immune regulatory pathways were upregulated, and both the galectin and annexin signaling modules lit up, including NAMPT, IL16, GRN, and CCL5 interactions converging on the same LGALS9 and ANXA1 nodes.

The convergence of those two pathways in both muscle and blood is the study’s most striking molecular claim, positioning LGALS9-CD45/CD44 and ANXA1-FPR1 as candidate pathogenic hubs in LGMD R12. The authors are careful about the apparent contradiction with the clean biopsy, offering two explanations: the sampled region may simply have missed infiltrating immune cells, and mild neurogenic injury detected in the left gastrocnemius by electromyography may have been sufficient to trigger inflammatory signaling. They also acknowledge the study’s central limitation, that the activation of these signaling pathways could not be experimentally verified for want of animal or cell models, and that findings from a single patient, however deeply profiled, cannot establish population-level conclusions.

Still, the work represents a genuine first. By constructing single-cell transcriptomic atlases of both diseased muscle and circulating immune cells from an LGMD R12 patient, the team has generated a mechanistic map that bulk RNA studies could never deliver, one that links a specific frameshift mutation to progenitor cell differentiation failure, fiber type loss, metabolic reprogramming, and systemic immune activation within a single framework. The raw data and analysis scripts have been deposited in public repositories, inviting the community to reanalyze and extend the findings. Whether the expanded muscle progenitor cells can be coaxed to mature, whether the metabolic decline can be pharmacologically slowed, and whether the galectin and annexin signaling hubs can be therapeutically intercepted are now testable questions. For a rare disease with no approved treatment, a single deeply profiled patient may have just supplied the research agenda for the next decade.

Subject of Research: Single-cell transcriptomic profiling of muscle and blood in a patient with ANO5-related limb-girdle muscular dystrophy type R12

Article Title: Single-cell transcriptome analysis of muscle and blood tissues from a patient with a rare homozygous ANO5 variant causing limb-girdle muscular dystrophy type R12

Article References: Chen, M., Dong, G., Wang, Y., Liu, J., Wang, Z., Bao, D., Huang, Z., Li, X., Li, Y., Cai, Z., & Wei, W. (2026). Single-cell transcriptome analysis of muscle and blood tissues from a patient with a rare homozygous ANO5 variant causing limb-girdle muscular dystrophy type R12. Frontiers in Genetics, 17, Article 1833196. https://doi.org/10.3389/fgene.2026.1833196

Image Credits: AI Generated

DOI: 10.3389/fgene.2026.1833196

Keywords: LGMD R12, ANO5, single-cell RNA sequencing, muscular dystrophy, muscle progenitor cells, MYH7, metabolism, immunology, LGALS9, ANXA1, genetics, rare disease

The biology behind this adverse reaction begins with the normal physiology of interleukin-6, a signaling molecule that acts on hepatocytes to drive the acute-phase response. When inflammation flares, IL-6 prompts the liver to ramp up production of fibrinogen, C-reactive protein, and other acute-phase proteins, which is why fibrinogen levels typically rise during active inflammatory states. Tocilizumab interrupts this pathway by binding the IL-6 receptor, and the resulting suppression of hepatic fibrinogen synthesis is generally regarded as a pharmacological effect rather than an idiosyncratic reaction. In most patients this effect is modest and clinically silent, but in a subset the decline is pronounced enough to constitute hypofibrinogenemia, defined in many laboratories as a concentration below 1.5 g/L. The case patient’s pretreatment value of 3.29 g/L sat comfortably within the normal range, and her fall to 0.85 g/L within roughly a month of re-exposure represents a drop of more than seventy percent, a magnitude that would ordinarily raise concern about spontaneous bleeding even though none was observed.

What makes the fibrinogen decline during tocilizumab therapy difficult to interpret at the bedside is that the drug simultaneously suppresses inflammation, which would normally be expected to lower fibrinogen toward baseline rather than below it. The distinction lies in the degree and tempo of the fall. A gradual drift from a mildly elevated value back toward the normal range is expected with effective anti-inflammatory treatment, whereas a steep descent below the reference interval, particularly one that continues after inflammatory markers have already normalized, suggests that IL-6 receptor blockade has unmasked or exaggerated an underlying limitation in fibrinogen production. In this patient, the concurrent laboratory picture offered some reassurance: liver enzymes remained essentially normal at both nadirs, with AST of 24 U/L and ALT of 14 U/L at the first nadir and 29 and 19 U/L at the second, arguing against hepatic synthetic failure as an alternative explanation. Albumin was mildly low at 31.3 g/L, which could reflect chronic disease and inflammation, but the isolated and reproducible nature of the fibrinogen decline, together with its reversal after drug withdrawal, points to a drug-related mechanism rather than a deteriorating liver.

The coagulation profile obtained at the second nadir adds further nuance. Prothrombin time was 11.8 seconds with an international normalized ratio of 0.97, and activated partial thromboplastin time was 21.6 seconds, both within conventional limits. This apparent paradox, in which fibrinogen is markedly reduced yet standard clotting times remain normal, is well recognized. Clotting assays are calibrated against pooled normal plasma, and because fibrinogen is the final common substrate of both the intrinsic and extrinsic pathways, these times often remain preserved until fibrinogen falls to extremely low concentrations, sometimes below 0.5 g/L. Thrombin time, which was prolonged at 25.5 seconds, is more sensitive to fibrinogen availability and can serve as an early clue. The elevated D-dimer of 3,626 μg/L FEU reflects ongoing fibrin turnover, which may be driven by the inflammatory state itself, and complicates the interpretation of fibrinogen dynamics because consumption and impaired production can coexist. Clinicians monitoring patients on tocilizumab therefore cannot rely on routine clotting screens alone and should consider direct fibrinogen measurement when unexplained bruising, mucosal bleeding, or laboratory anomalies appear.

The management decisions in this case illustrate the limited evidence base guiding treatment of tocilizumab-associated hypofibrinogenemia. After the first episode, the team withheld the drug and administered 20 units of cryoprecipitate, a plasma-derived concentrate rich in fibrinogen, factor VIII, von Willebrand factor, and factor XIII. Fibrinogen rose from 0.85 to 1.99 g/L within two days, but the subsequent trajectory, with values of 1.49, 1.85, and 2.07 g/L over the following seven weeks in the absence of further replacement, indicates that endogenous hepatic synthesis recovered once the pharmacological brake was removed. Notably, after the second episode the team chose observation alone, and fibrinogen still climbed from 1.05 to 1.28 g/L and then to 2.45 g/L by late September without any replacement therapy. This spontaneous recovery on both occasions reinforces the view that the effect is reversible and dose-dependent, and it suggests that cryoprecipitate is generally reserved for patients with very low levels or active bleeding rather than administered reflexively.

The question of whether dose reduction can prevent recurrence is central to this report, because it has never been clearly answered in the literature. The patient originally received 400 mg intravenously every four weeks, a dose below the standard 8 mg/kg regimen for her 56 kg body weight, which would have been approximately 448 mg. The rechallenge dose of 240 mg represented a forty percent reduction, yet hypofibrinogenemia still developed, albeit less severely, with a nadir of 1.05 g/L compared with 0.85 g/L during the first episode. The interval to nadir was also compressed, occurring 17 days after re-exposure rather than roughly a month. One plausible interpretation is that the first episode in 2026 was itself a recurrence of an unappreciated effect during the initial treatment course in 2024, when the patient received tocilizumab for about six months. Fibrinogen values recorded that year ranged from 2.21 to 4.36 g/L without a persistent downward pattern, but the available measurements may have been too infrequent to capture transient dips, and the drug was stopped for financial reasons rather than for safety concerns. If true, this would suggest that susceptibility to the effect is a stable individual trait rather than a random event, and that prior tolerance does not guarantee future tolerance.

The patient’s broader clinical context deserves attention because several features may have modulated her risk. She had a 13-year history of seropositive rheumatoid arthritis with high-titer rheumatoid factor and anti-cyclic citrullinated peptide antibodies, coexisting interstitial lung disease that precluded methotrexate, and a treatment history marked by intolerance and complications, including cervical lymph-node tuberculosis during infliximab therapy and a pruritic rash on iguratimod. Intermittent thrombocytopenia predated the 2026 tocilizumab reinitiation and persisted throughout, with platelet counts declining from 60 to 50 × 10^9/L across the observation period. Thrombocytopenia and hypofibrinogenemia together would ordinarily compound bleeding risk, yet the patient remained free of clinically evident bleeding at every stage, which is somewhat reassuring but also reflects the fact that fibrinogen levels above 1.0 g/L are often sufficient for hemostasis in stable patients. A bone marrow examination was considered but deferred because of the bleeding risk associated with severe thrombocytopenia, leaving the platelet decline without a definitive explanation, though chronic inflammation and drug effects are both plausible contributors.

From a surveillance standpoint, the case supports a practical monitoring framework for clinicians using tocilizumab. Because fibrinogen is not part of most standard pre-infusion panels, it may be worth adding to the laboratory schedule for patients beginning therapy, establishing a baseline against which later values can be judged. The timing of the declines in this patient, roughly three to four weeks after infusion in the first episode and just over two weeks after rechallenge, suggests that a check performed midway between infusions would be well positioned to catch a developing nadir before it becomes severe. The absence of bleeding symptoms in both episodes should not breed complacency, since spontaneous hemorrhage becomes a realistic concern once fibrinogen falls below approximately 0.5 to 1.0 g/L, particularly in elderly patients who may have additional vascular fragility or who require anticoagulation for comorbid conditions.

The causality assessment performed by the authors, using both the Naranjo algorithm and the WHO-UMC criteria, yielded a probable rating, which is the highest category typically achievable in the absence of rechallenge data, and the deliberate rechallenge here strengthens the inference considerably. The temporal sequence is clear, the effect reproduced at a lower dose, and alternative explanations such as liver disease, disseminated intravascular coagulation, or consumptive coagulopathy were reasonably excluded by the laboratory findings. The Naranjo algorithm assigns points for previously reported reactions, and hypofibrinogenemia during tocilizumab therapy has indeed been described in case series and real-world cohorts, though the frequency, severity thresholds, and management approaches vary widely across studies. Some real-world analyses suggest the phenomenon is not rare, which raises the question of whether routine fibrinogen monitoring should be considered for all patients on long-term IL-6 blockade rather than only for those with symptoms.

For patients like this woman, whose disease remained highly active with a DAS28 of 5.8 despite prednisone, iguratimod, and Tripterygium wilfordii, the therapeutic options after tocilizumab withdrawal are constrained. Her prior intolerance to iguratimod at higher exposure, her contraindication to methotrexate because of interstitial lung disease, and her adverse experience with a tumor necrosis factor inhibitor narrow the field considerably. Other biologics with different mechanisms, such as B-cell depletion or T-cell costimulation blockade, or targeted synthetic agents, may be considered, each with its own risk profile in a patient with interstitial lung disease and a history of tuberculosis. The decision to rechallenge with tocilizumab at a reduced dose was a reasoned attempt to retain clinical benefit while limiting toxicity, and the improvement in joint symptoms alongside the fall in inflammatory markers, with erythrocyte sedimentation rate dropping from 34 to 10 mm/h and C-reactive protein from 9.05 to 1.21 mg/L, confirms that even the reduced dose retained substantial efficacy. The trade-off, however, was a predictable recurrence of the fibrinogen decline, and the ultimate decision to withhold the drug again reflects the difficulty of balancing disease control against an adverse effect that, while rarely symptomatic in this patient, carries the potential for serious hemorrhagic complications if left unmonitored.

The broader lesson from this report is that hypofibrinogenemia during tocilizumab therapy deserves a place in the differential diagnosis of abnormal coagulation tests in treated patients, and that a prior episode should prompt heightened vigilance rather than reassurance if re-exposure is attempted. Dose reduction, while intuitively appealing, did not prevent recurrence here, and the compressed interval to the second nadir suggests that susceptibility may persist or even intensify with repeated exposure. Until larger datasets clarify which patients are at highest risk and whether any dosing strategy can reliably avoid the effect, individualized monitoring of fibrinogen, particularly in the weeks following initiation or reinitiation, remains the most defensible approach for clinicians managing patients who require this otherwise effective therapy.

Subject of Research: Recurrent tocilizumab-associated hypofibrinogenemia in rheumatoid arthritis after reduced-dose rechallenge

Article Title: Recurrent hypofibrinogenemia after reduced-dose tocilizumab rechallenge in rheumatoid arthritis: a case report

Article References: Li, Y., Yan, Y., Zhou, H., Fu, E., & Zheng, M. (2026). Recurrent hypofibrinogenemia after reduced-dose tocilizumab rechallenge in rheumatoid arthritis: a case report. Frontiers in Pharmacology, 17, 1981054. https://doi.org/10.3389/fphar.2026.1981054

Image Credits: AI Generated

DOI: 10.3389/fphar.2026.1981054

Keywords: tocilizumab, hypofibrinogenemia, rheumatoid arthritis, interleukin-6, fibrinogen, drug safety, case report, rechallenge, pharmacovigilance, biologic therapy, coagulation, immunology

Mitochondrial quality control is the cell’s system for monitoring and maintaining the health of its mitochondria, the organelles that generate energy through the electron transport chain. When mitochondria are damaged, they produce excess reactive oxygen species and leak inflammatory signals, a process increasingly linked to autoimmune diseases. In rheumatoid arthritis, dysfunctional mitochondria have been implicated in the activation of fibroblast-like synoviocytes and the production of inflammatory cytokines, but the specific genes governing this quality control system in the disease had remained poorly characterized.

The research team, led by Yuting Xiao and Jing Wu, assembled an unusually broad dataset for this kind of analysis. They integrated two bulk blood transcriptomic datasets comprising 248 samples from patients with rheumatoid arthritis and 88 controls, alongside a single-cell RNA sequencing dataset of peripheral blood mononuclear cells containing 11,719 individual cells from three patients and three healthy donors. This dual approach allowed them to capture both the average gene expression patterns across whole blood and the cell-type-specific behaviour of individual immune cells.

To narrow down the candidates, the researchers used weighted gene co-expression network analysis, a computational method that groups genes into modules based on correlated expression patterns across samples. They combined this with differential expression analysis and then applied three machine-learning algorithms: least absolute shrinkage and selection operator regression, support vector machine-recursive feature elimination, and random forest classification. The convergence of these independent methods on a small set of genes gave the team confidence that the findings were not statistical artefacts.

Nine mitochondrial quality control-related candidate genes survived this gauntlet of computational filters. After further validation, CDC42 and RBBP7 stood out as the most compelling. CDC42, a gene encoding a small signalling protein involved in cell shape and movement, was upregulated in patients with rheumatoid arthritis, while RBBP7, part of a chromatin-remodelling complex, was downregulated. The team confirmed these expression patterns using reverse transcription quantitative polymerase chain reaction on independent samples.

Gene set enrichment analysis revealed that CDC42 was linked to JAK-STAT signalling, a pathway already targeted by existing rheumatoid arthritis drugs such as tofacitinib. Translation initiation, by contrast, showed opposite enrichment patterns between the two genes. The finding that CDC42 connects to a druggable pathway raises the possibility that mitochondrial quality control and established inflammatory signalling are intertwined in the disease, rather than operating as separate processes.

After correcting for multiple testing, the researchers found that 15 immune cell subsets differed significantly between patients and controls. Monocytes, a type of white blood cell that floods inflamed joints in rheumatoid arthritis, showed a positive correlation with CDC42 and a negative correlation with RBBP7. This pattern suggests that the two genes may help shape the inflammatory behaviour of monocytes, which are central players in the joint destruction characteristic of the disease.

The single-cell analysis added an unexpected layer to the story. RBBP7 showed relatively high expression in B cells, the antibody-producing cells of the immune system. This prompted the team to conduct exploratory analyses of B cell trajectories, metabolic states, and predicted communication between B cells and monocytes through the CCL5-CCR1 signalling pair. While these findings remain preliminary, they hint that mitochondrial quality control genes may influence how different immune cell populations talk to each other in the bloodstream.

The study’s strength lies in its multi-layered validation strategy, combining bulk sequencing, single-cell resolution, machine learning, immune cell deconvolution, metabolic profiling, and experimental confirmation. However, the work remains observational and correlational. The samples came from blood rather than joint tissue, and the B cell findings are explicitly exploratory. The authors note that further functional studies will be needed to determine whether CDC42 and RBBP7 drive rheumatoid arthritis pathology or simply mark its presence.

Nevertheless, the identification of two mitochondrial quality control genes with such distinct immune and metabolic signatures offers a fresh angle on a disease that affects millions worldwide. If future research confirms that these genes actively shape monocyte behaviour or B cell communication, they could become targets for new diagnostics or therapies, adding a mitochondrial dimension to the immunological understanding of rheumatoid arthritis.

The connection between mitochondrial dysfunction and rheumatoid arthritis has been building for years, but the new study adds a gene-level map to what has largely been a phenomenological picture. Mitochondria in immune cells do more than produce ATP; their permeability transition, their release of mitochondrial DNA, and their turnover through mitophagy all feed into innate immune signalling. When quality control falters, damaged organelles accumulate and can sustain the production of inflammatory mediators. The identification of CDC42 and RBBP7 as differentially expressed genes within this machinery suggests that the disease may exploit specific molecular nodes rather than a diffuse breakdown of mitochondrial housekeeping.

CDC42 is a particularly interesting candidate in this context. As a member of the Rho family of small GTPases, it orchestrates actin polymerisation, cell polarity, and migration, processes that are directly relevant to how immune cells move through tissue and form the synovial infiltrates characteristic of rheumatoid arthritis. Its established role in T cell activation and in the cytoskeletal rearrangements that accompany monocyte trafficking provides a plausible mechanistic bridge between a mitochondrial quality control signature and the immune cell behaviour observed in the study. The reported link to JAK-STAT signalling, a pathway already exploited therapeutically, raises the question of whether CDC42 sits at a junction where metabolic stress is translated into cytokine-driven transcriptional programmes.

RBBP7 presents a different kind of puzzle. As a core component of histone-binding and chromatin-remodelling complexes, it operates at the level of gene regulation rather than signalling. Its downregulation in patients, together with its relatively high expression in B cells among the single-cell data, suggests that epigenetic states may vary across immune populations in ways that intersect with mitochondrial quality control. The exploratory analyses of B cell trajectories and metabolism, while preliminary, point toward a possible axis in which altered chromatin regulation, metabolic state, and intercellular communication through CCL5-CCR1 shape how B cells and monocytes interact in peripheral blood.

The immune cell deconvolution findings deserve particular attention. Fifteen immune cell subsets differing between patients and controls after multiple-testing correction is a substantial number, reflecting the broad immunological remodelling that accompanies active disease. The specific correlation pattern, with monocytes tracking positively with CDC42 and negatively with RBBP7, is consistent with the known importance of monocytes and their derived macrophages in driving joint inflammation. Monocytes are also metabolically plastic cells, shifting between oxidative phosphorylation and glycolysis as they activate, which makes them a natural setting in which mitochondrial quality control genes might influence function.

Methodologically, the study illustrates the growing standard in computational immunology of triangulating across independent algorithms. Each machine-learning approach has distinct biases: LASSO regression favours sparse solutions, support vector machine-recursive feature elimination iteratively removes weak features, and random forest captures nonlinear interactions. Requiring convergence across all three reduces the risk that any single algorithm’s preferences drive the final gene list. Combining this with co-expression network analysis and single-cell validation adds further layers of confidence, though it cannot substitute for the functional experiments that would establish causality.

The choice of peripheral blood rather than synovial tissue is both a strength and a limitation. Blood is accessible and allows for larger sample sizes, as reflected in the 248 patient samples analysed here. But the joint is where the disease manifests, and the local immune and stromal environment, including fibroblast-like synoviocytes, may express mitochondrial quality control genes differently from circulating cells. Future studies using synovial biopsies or single-cell analysis of joint tissue would help determine whether the blood-based signatures mirror what happens at the site of pathology.

The RT-qPCR confirmation on independent samples is an important step that many bioinformatic studies omit. It demonstrates that the expression differences are not artefacts of batch effects or platform-specific noise. Still, mRNA abundance does not always track protein levels or functional activity, and CDC42 in particular is heavily regulated post-translationally. Measuring protein abundance and activity states would strengthen the case that these genes are not just correlated with disease but actively involved in it.

Looking forward, the most valuable next steps would be perturbation experiments. Knocking down or overexpressing CDC42 and RBBP7 in monocyte or B cell models, and then measuring mitochondrial membrane potential, reactive oxygen species production, mitophagy flux, and cytokine output, would clarify whether these genes are drivers or passengers. Similarly, testing whether JAK-STAT inhibitors modulate CDC42 expression or mitochondrial quality control readouts in patient cells could reveal whether existing therapies already engage this axis. Such work would move the findings from association toward mechanism and clarify whether the mitochondrial quality control signature has genuine therapeutic or prognostic value.

Subject of Research: Integrating bulk and single-cell RNA sequencing to identify mitochondrial quality control-related key genes in rheumatoid arthritis

Article Title: Integrating bulk and single-cell RNA sequencing to identify mitochondrial quality control-related key genes in rheumatoid arthritis

Article References: Xiao, Y., zhang, J., Su, J., & Wu, J. (2026). Integrating bulk and single-cell RNA sequencing to identify mitochondrial quality control-related key genes in rheumatoid arthritis. Scientific Reports. https://doi.org/10.1038/s41598-026-76389-w

Image Credits: AI Generated

DOI: 10.1038/s41598-026-76389-w

Keywords: rheumatoid arthritis, mitochondrial quality control, CDC42, RBBP7, single-cell RNA sequencing, immunology, Integrating, bulk, single-cell, sequencing, identify, mitochondrial

The scientific case rests on a remarkable convergence of biological properties. Zebrafish embryos develop outside the mother, with most organs forming within 24 hours of fertilization, and remain optically transparent for the first few days of life. This allows researchers to watch organogenesis, tumor growth, immune cell migration, and cardiac function unfold in real time inside a living vertebrate. A single breeding pair produces hundreds of eggs per week, fish reach sexual maturity in roughly three months, and maintenance costs are a fraction of those for mammalian colonies. Crucially, around 80 percent of human disease-linked genes have zebrafish orthologs, and core molecular processes—signal transduction, endocrine regulation, immune responses, and xenobiotic metabolism—are highly conserved, including functional counterparts of key drug-metabolizing enzymes and transporters. Modern genome-editing tools such as CRISPR/Cas9, Cre-lox systems, and transgenesis have all been adapted for the fish, enabling precise disease modelling and high-throughput in vivo screening at a scale unattainable in rodents.

The ethical architecture of the recommendations is anchored in the 3Rs framework of Replacement, Reduction, and Refinement, now extended by proposals for a fourth R, Responsibility, and a fifth R, Rehoming. The Society specifically recommends using embryos and larvae up to the stage preceding independent feeding—commonly around five days post-fertilization—for in vivo experiments. This timing matters legally as much as ethically: EU Directive 2010/63/EU defines its scope of protection with reference to independently feeding larval forms, meaning zebrafish embryos and early larvae fall outside the Directive’s formal scope. Polish national legislation, through the Act of 15 January 2015 on the protection of animals used for scientific or educational purposes, mirrors this exclusion. In practical terms, experiments on zebrafish embryos and early larvae may constitute a genuine legal alternative to classical protected-stage experiments, contributing to the replacement or reduction of mammalian models where scientifically appropriate. When later developmental stages or adult fish are required, the Society insists on approval from the competent Local Ethics Committee for Animal Experiments.

Nowhere is the model’s power more vivid than in oncology. The Society recommends the human-zebrafish xenograft approach, in which human cancer cells—from established lines or directly from patients—are implanted into zebrafish embryos or larvae. Because the larval immune system is not yet fully functional during the first days of life, human cells engraft and proliferate without immunosuppression. The transparent body permits direct visualization of tumor development, angiogenesis, and metastasis at single-cell resolution, and unlike in mouse models, human cancer cells in zebrafish readily migrate and form metastases, allowing drug effects on this critical aspect of tumor biology to be assessed under true in vivo conditions. Xenograft experiments can be completed in less than a week, whereas analogous mouse studies typically require several weeks. This so-called Avatar strategy is already entering clinical contexts: in a translational study involving breast cancer patients, complete concordance was demonstrated between chemotherapy responses observed in the larval model and the actual clinical responses, confirming high predictive value for personalized medicine. The model has also delivered clinically validated drugs—larval zebrafish studies revealed thalidomide’s strong inhibitory effect on tumor angiogenesis through suppression of VEGF signaling, helping establish thalidomide and its derivatives as therapies for neovascularization-dependent cancers such as multiple myeloma.

In toxicology, the recommendations position zebrafish as a tiered pre-filter for chemical and pharmaceutical safety. The Fish Embryo Acute Toxicity Test, standardized under OECD TG 236, determines lethal concentration values over a 96-hour exposure window in embryos, providing early hazard identification without adult vertebrates. While LC50 endpoints are not directly equivalent to rodent LD50 values, they deliver comparable information on acute toxicity and are primarily used for screening and prioritization rather than direct regulatory substitution. Embryonic transparency enables direct observation of teratogenic and embryotoxic potential, revealing morphological abnormalities, oxidative stress, apoptosis, and endocrine disruption induced by pharmaceuticals or contaminants. The assay’s compatibility with multi-well plate formats, robotic microscopes, computerized readers, and artificial intelligence allows automated detection of embryo orientation and organ-specific analysis of the heart, brain, or vessels. Regulatory recognition is growing: the FET assay is incorporated into OECD guidelines as an accepted alternative for chemical safety assessment, the US Food and Drug Administration acknowledges zebrafish for investigative and early-screening preclinical procedures, and the European Medicines Agency has expressed strong interest in preliminary regulatory reviews. The Society cautions, however, that zebrafish should not be regarded as a universal replacement where regulatory frameworks demand mammalian data on pregnancy, lactation, multigenerational endpoints, or long-term systemic organ toxicity.

Neurology and neuropsychiatry showcase the model’s translational depth. Zebrafish possess a hypothalamic–pituitary–interrenal axis homologous to the mammalian stress axis, with conserved cortisol synthesis, alongside well-organized serotonergic, dopaminergic, glutamatergic, and GABAergic neurotransmitter systems. Epilepsy research has been transformed by two complementary approaches: seizures can be induced in larvae with pentylenetetrazole, and genetic models based on the scn1lab gene—which corresponds to the human SCN1A gene mutated in Dravet syndrome—faithfully recapitulate reduced GABAergic signaling, spontaneous seizures, and abnormal neuronal activity. High-throughput phenotypic screening in multi-well formats using automated locomotor tracking and local field potential recordings identified clemizole as a potent seizure suppressor in the scn1lab model, and the same pipeline has highlighted serotonergic modulators such as fenfluramine and unexpected compound classes including synthetic cannabinoids. Classical antidepressants like fluoxetine and citalopram induce behavioral effects in zebrafish consistent with their human actions, and standardized larval assays—open-field thigmotaxis, light–dark preference, and light–dark challenge tests—quantify anxiety-like behavior with high predictive value. Social behavior assays in older larvae and juveniles have even been applied to model neurodevelopmental conditions relevant to autism spectrum disorders.

Metabolic disease research exploits the model’s conserved endocrine machinery. Zebrafish retain homologous insulin, glucagon, nuclear receptors, and appetite-regulating pathways; more than 70 percent of carbohydrate and glucose metabolic genes are conserved across zebrafish, frog, chicken, mouse, and human, with 57 percent linked to human type 2 diabetes. Larval insulin resistance models generated through elevated glucose, dexamethasone, or exogenous insulin exposure display features of impaired glucose handling suitable for evaluating antidiabetic drug candidates. For type 1 diabetes, transgenic lines expressing nitroreductase under the insulin promoter enable inducible, highly specific beta cell destruction upon metronidazole exposure, producing reproducible insulin deficiency and hyperglycemia while allowing real-time visualization of pancreatic islet regeneration. Adult fish on high-fat or high-cholesterol diets develop obesity, dyslipidemia, and atherosclerosis-like vascular lipid accumulation with conserved lipoprotein metabolism and inflammatory pathways. Storage diseases are equally tractable: the zebrafish model of Fabry disease, lacking alpha-galactosidase A activity, revealed an independent mechanism of kidney damage driven by mitochondrial alterations and disturbed glycolysis and galactose metabolism, beyond the canonical lysosomal accumulation of globotriaosylceramide.

Immunology and cardiology round out the model’s portfolio with distinctive technical advantages. During the first week of life, zebrafish larvae possess only a functional innate immune system, with adaptive immunity developing weeks later—a temporal separation that permits selective investigation of neutrophil and macrophage responses without adaptive interference. Transgenic reporter lines such as Tg(mpx:GFP) for neutrophils and Tg(mpeg1:mCherry) for macrophages enable direct visualization of leukocyte migration and host–pathogen interactions in living organisms. Infection of larvae with Mycobacterium marinum, closely related to Mycobacterium tuberculosis, recapitulates the hallmark organized granulomas of human tuberculosis and has enabled identification of virulence factors, host defense mechanisms, and high-throughput screening for novel antitubercular drugs, while reporter lines tracking autophagy marker LC3 recruitment to bacterial vacuoles illuminate cell-autonomous immunity against Staphylococcus aureus and Salmonella Typhimurium. In cardiology, homologs of key cardiac ion channels including hERG make zebrafish respond to QT-prolonging drugs comparably to humans: a landmark study identified 22 of 23 clinically relevant proarrhythmic compounds as positive in the assay, a drug-sensitized screen uncovered 15 genes affecting cardiac repolarization including GINS3, and screening of 3,000 compounds in a doxorubicin-induced cardiomyopathy model yielded the cardioprotective molecules visnagin and diphenylurea, subsequently validated in mice. Adult zebrafish uniquely regenerate cardiac muscle after injury through cardiomyocyte dedifferentiation and proliferation—a capacity absent in mammals—making the fish an unmatched system for heart regeneration research.

The recommendations arrive against a sobering backdrop of preclinical failure. The overall preclinical-to-market attrition rate exceeds 92 percent, a figure unchanged for three decades. Mouse models produce positive preclinical results in 90 to 95 percent of studies, yet fewer than 8 to 10 percent translate to approved drugs, falling to 3.5 percent in oncology—a gap attributed less to mouse biology than to study design, publication bias, sex bias, lack of genetic diversity, and failure to reproduce the full complexity of human immunology and metabolism. Notably, zebrafish under 120 hours post-fertilization, which do not swim or feed independently, are considered New Alternative Methodologies under EU Directive 2010/63, and the FDA has developed a draft on NAM use in preclinical research paving the way for zebrafish in these studies. The Society frames the fish as the most productive early-stage preclinical pipeline: an intermediate platform positioned between simple in vitro systems and resource-intensive mammalian studies, used to prioritize compounds, identify early toxicity signals, and refine hypotheses before mammalian validation. Implementation, the authors stress, requires question-driven design, standardized protocols with defined developmental stages, exposure windows, and controls, robust biologically relevant endpoints, and predefined criteria for progression to mammalian models. With zebrafish now the second most frequently used animal model in EU research after mice, the Society calls on research institutions, pharmaceutical companies, and regulatory agencies to systematically incorporate these embryo and larval assays into efficacy and safety evaluation, grant applications, and research standards—an integration the authors argue will yield more humane, efficient, and innovative science, ultimately benefiting medical progress and public health.

Subject of Research: Use of the zebrafish (Danio rerio) model in biomedical research and its recommendations for replacing mammalian models

Article Title: Recommendations of the Polish Zebrafish Society on the use of the zebrafish (Danio rerio) model in biomedical research

Article References: Podlasz, P., Migocka-Patrzałek, M., Prajsnar, T. K., Sarosiak, A., & Tylzanowski, P. (2026). Recommendations of the Polish Zebrafish Society on the use of the zebrafish (Danio rerio) model in biomedical research. Acta Biochimica Polonica, 73, Article 16545. https://doi.org/10.3389/abp.2026.16545

Image Credits: AI Generated

DOI: 10.3389/abp.2026.16545

Keywords: zebrafish, Danio rerio, 3Rs principles, preclinical research, drug discovery, toxicology, oncology, xenograft, cardiotoxicity, epilepsy, diabetes, immunology

The challenge the researchers set out to tackle is well known in rheumatology. Current biomarkers, including rheumatoid factor and anti-cyclic citrullinated peptide antibodies, demonstrate limited sensitivity and fail to reliably reflect fluctuations in disease activity. Because rheumatoid arthritis is highly heterogeneous, with synovial inflammation driven by coordinated action of many genes involved in recruiting various immune cells to the inflammatory site, single-marker approaches have repeatedly fallen short. Early diagnosis matters enormously, since timely intervention is needed to prevent irreversible structural joint damage and disability caused by pannus formation, in which hyperplastic synovial tissue invades cartilage and bone.

To build a more robust analytical foundation, the team downloaded three gene expression datasets from the Gene Expression Omnibus database: GSE55457, GSE12021 and GSE77298, all derived from human synovial tissue samples. Because the datasets came from different studies and microarray platforms, they first corrected for batch effects using the ComBat function of the sva package in R. Principal component analysis before and after correction showed that the three datasets were initially separated by study, but post-ComBat normalization achieved better sample integration while the biological distinction between rheumatoid arthritis and healthy control samples remained evident. This step is critical, as technical variability between batches can otherwise masquerade as disease signal.

With the integrated matrix in hand, the researchers identified differentially expressed genes using the limma package, applying linear models with empirical Bayes moderation and selecting genes with an absolute log2 fold change greater than 1 and an adjusted p-value below 0.05 according to the Benjamini-Hochberg method. The analysis yielded 440 differentially expressed genes, comprising 243 upregulated and 197 downregulated genes in rheumatoid arthritis synovium. Genes associated with immune response processes, such as chemokines and cytokine receptors, were mostly upregulated, while genes related to metabolism and structural proteins were mostly downregulated. Functional enrichment analysis using Gene Ontology, KEGG and gene set enrichment analysis showed the differentially expressed genes were involved in inflammatory response, T-cell activation, B-cell receptor signaling, cytokine-cytokine receptor interaction, hematopoietic cell lineage, primary immunodeficiency and rheumatoid arthritis pathways.

The next stage narrowed the field through network analysis and machine learning. The top 100 differentially expressed genes, ranked by absolute logFC, were submitted to the STRING database to construct a protein-protein interaction network, which was visualized and analyzed in Cytoscape. The maximum clique centrality algorithm in the cytoHubba plugin identified the top 20 genes as hub candidates, most associated with immune cells, chemokine signaling and inflammatory responses. Two complementary machine learning algorithms then filtered these candidates. LASSO logistic regression, fitted with the glmnet package and stratified 10-fold cross-validation, shrank the coefficients of most candidate genes to zero as the regularization parameter increased; under the lambda.1se criterion, only CXCL13 and CXCL10 retained non-zero coefficients. Support vector machine-recursive feature elimination, run with a linear SVM classifier and stratified five-fold cross-validation repeated 10 times, independently converged on the same two genes. The training dataset consisted of 41 rheumatoid arthritis and 26 healthy control samples, and all feature selection was performed exclusively on this data.

Diagnostic performance was assessed through receiver operating characteristic curve analysis. In the training set, CXCL13 produced an area under the curve of 0.954, with an accuracy of 89.6 percent, a sensitivity of 85.4 percent, a specificity of 96.2 percent and an F1 score of 90.9 percent. CXCL10 produced an AUC of 0.925, with an accuracy of 88.1 percent, a sensitivity of 87.8 percent, a specificity of 88.5 percent and an F1 score of 90.0 percent. The researchers then evaluated the biomarkers in an independent RNA-seq validation dataset, GSE89408, comprising 152 rheumatoid arthritis and 28 healthy control samples, which was not involved in any feature selection or modeling procedure. Although performance was somewhat lower in the validation cohort, the genes retained good diagnostic value: CXCL13 achieved an AUC of 0.901 with 81.7 percent accuracy, while CXCL10 achieved an AUC of 0.886 with 78.9 percent accuracy and a striking 96.4 percent specificity.

Beyond diagnosis, the study probed the mechanistic dimension of these biomarkers using CIBERSORTx, a digital cytometry tool that estimates the relative abundance of 22 immune cell subsets from bulk tissue expression data using the LM22 signature matrix. All 67 samples satisfied the deconvolution quality criterion. Compared with healthy subjects, rheumatoid arthritis synovium showed significantly increased infiltration of plasma cells, T follicular helper cells, gamma delta T cells, monocytes and M1 macrophages, along with decreased resting mast cells. Spearman correlation analysis, adjusted for multiple testing, revealed strong positive associations between the hub genes and infiltrated immune cells: CXCL10 expression correlated with M1 macrophages at r = 0.83, while CXCL13 correlated with M1 macrophages at r = 0.75 and with gamma delta T cells at r = 0.72. CXCL13 was associated with multiple immune cell populations, including plasma cells, T-cell subsets and M1 macrophages, whereas CXCL10 showed significant associations with M1 macrophages, plasma cells and selected T-cell subsets.

These correlation patterns carry biological weight. CXCL13 has previously been reported to be associated with B-cell migration and the formation of ectopic lymphoid structures in synovial tissue, while CXCL10 has been linked to T-cell migration and macrophage recruitment during inflammation. The researchers suggest that the corresponding receptor axes, CXCL13-CXCR5 and CXCL10-CXCR3, may represent potential target pathways warranting further investigation. Inhibiting CXCR3 and CXCR5 receptors on immune cells could block activation by other ligands within the multi-ligand, multi-receptor families of chemokines, offering a hypothesis for future therapeutic research. Notably, CXCL13 and CXCL10 have previously been examined in rheumatoid arthritis as baseline serum predictors of response to TNF-inhibitor therapy in a small prospective clinical cohort, but the present study differs in both aim and approach by establishing them as diagnostic biomarkers derived from synovial tissue transcriptomics.

The authors acknowledge limitations, noting that the analysis is based on microarray gene expression data, which may have inherent constraints, and that the unequal distribution of samples in the validation dataset means results were interpreted primarily based on ROC-AUC values as supportive rather than definitive evidence. Nevertheless, the integrative framework, combining batch-corrected multi-cohort gene expression data, dual machine learning feature selection and external validation in an independent RNA-seq dataset, provides an analytical platform that can be used to identify and validate potential biomarkers for heterogeneous autoimmune diseases. As synovial inflammation in rheumatoid arthritis is associated with the coordinated action of many genes involved in immune cell recruitment, CXCL13 and CXCL10 stand out as molecular signposts of the inflammatory storm within the joint, and their receptor pathways may guide the next generation of diagnostic and therapeutic exploration.

Subject of Research: Health

Article Title: Machine learning-based identification of CXCL13 and CXCL10 as key biomarkers in rheumatoid arthritis

Article References: M, S., S, S. A., M, S., P, N., Salau, A. O., Usman, A. G., & Yousfan, M. (2026). Machine learning-based identification of CXCL13 and CXCL10 as key biomarkers in rheumatoid arthritis. Frontiers in Bioinformatics, 6, Article 1925964. https://doi.org/10.3389/fbinf.2026.1925964

Image Credits: AI Generated

DOI: 10.3389/fbinf.2026.1925964

Keywords: machine learning, rheumatoid arthritis, biomarkers, CXCL13, CXCL10, bioinformatics, immunology, Machine, learning-based, identification, rheumatoid, arthritis

Infections are among the most feared complications of advanced liver disease. When cirrhosis decompensates—through ascites, variceal bleeding, or hepatic encephalopathy—an infection is frequently the trigger or the accelerant. Bacterial translocation from the gut, impaired clearance of microbes by the reticuloendothelial system, and systemic inflammation converge to make cirrhotic patients exquisitely susceptible. Once an infection takes hold, the clinical trajectory often steepens sharply: in the Graz cohort, patients who developed an infection faced a mortality rate of 41 percent during follow-up. Identifying who is most vulnerable before the first fever appears is therefore a central clinical challenge, and the standard prognostic instruments—the Model for End-stage Liver Disease (MELD) score and the Child-Pugh classification—capture liver dysfunction but say little about immune competence.

HDL and apolipoprotein A-I bring exactly that missing dimension. Far from being a passive cholesterol shuttle, HDL is an active participant in innate immunity. It binds and neutralizes lipopolysaccharide, the toxic lipid component of Gram-negative bacterial cell walls, sequestering it away from the lipopolysaccharide-binding protein pathway that would otherwise amplify inflammatory signaling. Apolipoprotein A-I, which constitutes roughly 70 percent of HDL protein mass, contributes to this endotoxin-binding capacity and also modulates leukocyte behavior, supporting anti-inflammatory polarization of monocytes and macrophages. In chronic liver disease, both the quantity and the quality of HDL deteriorate: hepatic lipase and lecithin-cholesterol acyltransferase activity decline, apolipoprotein composition shifts, and the particle becomes pro-inflammatory rather than protective. Low HDL-C in cirrhosis is thus not merely a metabolic footnote but a potential readout of a compromised endotoxin-buffering system.

The Graz team, led by Florian Rainer, Markus Trieb, Angela Horvath, Gunther Marsche, Vanessa Stadlbauer, and Rudolf E. Stauber, designed the study as a single-centre cohort with a built-in temporal validation. A total of 311 patients with cirrhosis were enrolled, divided into a training cohort of 225 and a separate validation cohort of 86 recruited later. At baseline, researchers measured HDL cholesterol and apolipoprotein A-I alongside standard clinical chemistry. The primary endpoint was strictly defined: an infection requiring antibiotic therapy within 12 months. Infections occurred in 24 percent of the training cohort and 31 percent of the validation cohort, consistent with the substantial infectious burden known to accompany decompensated cirrhosis.

The statistical machinery applied was appropriately rigorous for a prognostic biomarker study. Cox regression models estimated the association between baseline biomarker levels and time to first infection, producing both crude and adjusted hazard ratios. Discriminative performance was quantified with Harrell’s C-index and with censoring-adjusted, time-dependent receiver operating characteristic analyses at the 12-month horizon. When HDL-C or apoA-I were added to the MELD score in the training cohort, both biomarkers significantly improved discrimination, and the combined biomarker models achieved higher C-indices and numerically higher 12-month area-under-the-curve values than MELD or Child-Pugh alone. In other words, the lipid markers carried prognostic information that the established liver scores did not.

From the training data, the team derived exploratory cut-offs: HDL-C below 40.4 milligrams per deciliter and apoA-I below 98.5 milligrams per deciliter identified groups with higher infection risk. These thresholds sit close to conventional clinical boundaries for low HDL, suggesting that the biomarker signal is not confined to extreme values but operates across the range routinely seen in cirrhotic patients. Lower levels of both markers were significantly associated with infection risk in both the training and validation cohorts, lending the core association a degree of robustness that single-cohort findings often lack.

The validation results, however, temper the enthusiasm. In the 86-patient temporal validation cohort, the discriminative performance of the biomarker-based models attenuated: they performed comparably to, rather than better than, the established MELD and Child-Pugh scores. This pattern is familiar in biomarker research. Models fitted to one dataset routinely shrink when applied to another, as overfitting, cohort composition, disease stage, and chance all conspire to erode apparent performance. The Graz investigators are explicit about this limitation: the findings support HDL-C and apoA-I as candidate prognostic biomarkers of infection susceptibility, but external validation in independent centres and prospective assessment of clinical utility are required before any recommendation for routine use can be made.

The mechanistic interpretation is where the story becomes scientifically rich. Cirrhosis dismantles the liver’s role as the body’s endotoxin filter. Portal hypertension widens the gut mucosal barrier, allowing bacterial products to translocate into portal blood, while the diseased hepatic reticuloendothelial system clears them less efficiently. HDL, by binding lipopolysaccharide and promoting its delivery to the liver for detoxification, acts as a circulating countermeasure. When HDL-C and apoA-I fall—whether through impaired hepatic synthesis, malnutrition, inflammation-driven catabolism, or qualitative particle dysfunction—the endotoxin-buffering reserve thins. The result is a patient whose plasma can no longer adequately sequester bacterial toxins, priming the innate immune system for the exaggerated inflammatory responses that characterize spontaneous bacterial peritonitis and sepsis in cirrhosis. Low HDL in this context may be a biomarker of both a depleted defense and a liver too sick to rebuild it.

There are also therapeutic implications, though the authors are careful to label them as requiring dedicated investigation. HDL-raising interventions exist—niacin, statins, CETP inhibitors, lifestyle measures—but their history in cardiology is cautionary: raising HDL-C pharmacologically has repeatedly failed to translate into clinical benefit, and the qualitative functionality of the particle matters as much as its concentration. In cirrhosis, the relevant question is not whether HDL-C can be numerically elevated but whether the endotoxin-binding and immune-modulatory functions of apoA-I can be restored. Apolipoprotein A-I infusions and HDL-like synthetic particles have shown endotoxin-neutralizing capacity in experimental sepsis models, offering a speculative route from biomarker to therapy. Whether such approaches could reduce infection risk in cirrhotic patients remains an open question that no current evidence answers.

What the Graz study delivers now is a candidate risk stratification tool built from two inexpensive, widely available laboratory measurements. A clinician seeing a decompensated cirrhotic patient with HDL-C under 40 milligrams per deciliter and apoA-I under 100 milligrams per deciliter gains a signal—beyond MELD and Child-Pugh—that this individual sits in a higher infection-risk stratum and may warrant heightened surveillance, earlier diagnostic workup for subtle infection, and closer follow-up. The association between infection and a 41 percent mortality rate during follow-up underscores the stakes. Until external validation confirms the cut-offs and prospective trials demonstrate that acting on them improves outcomes, HDL-C and apoA-I remain promising candidates rather than established instruments. But the study adds a compelling chapter to the growing recognition that lipoproteins are not just cardiovascular currency—they are immunological actors whose decline in cirrhosis may announce, months in advance, the infections that decompensate and kill.

Subject of Research: Lipoprotein-related biomarkers HDL-C and apoA-I predict infection risk in patients with liver cirrhosis

Article Title: Lipoprotein-related biomarkers HDL-C and apoA-I predict infection risk in patients with liver cirrhosis

Article References: Rainer, F., Trieb, M., Horvath, A., Douschan, P., Scharnagl, H., Heinemann, Á., Marsche, G., Stadlbauer, V., & Stauber, R. E. (2026). Lipoprotein-related biomarkers HDL-C and apoA-I predict infection risk in patients with liver cirrhosis. Scientific Reports. https://doi.org/10.1038/s41598-026-74841-5

Image Credits: AI Generated

DOI: 10.1038/s41598-026-74841-5

Keywords: liver cirrhosis, HDL cholesterol, apolipoprotein A-I, biomarkers, infection risk, immunology, Scientific Reports, Lipoprotein-related, HDL-C, apoA-I, predict, infection

Psoriasis is a chronic immune-mediated inflammatory skin disease driven largely by the interleukin (IL)-23/Th17 signaling axis, a pathway that modern immunology has identified as a central engine of the disease’s characteristic plaques and systemic inflammation. Tildrakizumab is a humanized monoclonal antibody engineered to bind selectively to the p19 subunit of IL-23, thereby interrupting IL-23-dependent Th17 responses while leaving upstream immune pathways largely intact. This selectivity is the drug’s conceptual appeal: it suppresses the pathogenic inflammation at the heart of psoriasis without the broader immune perturbation associated with agents that directly inhibit IL-17 or other cytokines.

The drug’s pedigree in trials is strong. In the pivotal phase III studies reSURFACE 1 and reSURFACE 2, tildrakizumab demonstrated robust efficacy and a favorable long-term safety profile in patients with moderate-to-severe plaque psoriasis, and a Japanese subgroup analysis plus a five-year extension study confirmed durable efficacy and tolerability in Japanese patients specifically. But trial populations are highly selected, and the gap between trial conditions and routine practice is precisely where real-world evidence becomes indispensable. Differences in baseline disease severity, prior treatments, and how outcomes are counted can dramatically reshape the apparent success of a therapy.

The Iwate team took a deliberately conservative approach. Between July 2021 and December 2025, 49 patients initiated tildrakizumab at their center; after excluding 8 patients treated without the approved loading regimen, 10 who had not yet reached 28 weeks of treatment, and 1 treated outside the approved dosing interval, 30 consecutive patients formed the analysis cohort. All received tildrakizumab 100 mg according to the approved Japanese regimen: subcutaneous injections at weeks 0 and 4, followed by maintenance dosing every 12 weeks. Disease severity was tracked with the Psoriasis Area and Severity Index (PASI) at weeks 0, 4, 16, 28, 40, and 52, with a visit window of plus or minus one week.

The cohort itself reflects the messy reality of dermatology clinics. The 30 patients included 22 men and 8 women, with a mean age of 57.3 years ranging from 26 to 81, a mean body weight of 69.44 kilograms, and a mean disease duration of 17.4 years. Twelve patients had a body mass index of 25 or higher, and 21 were current or former smokers. Thirteen had lived with psoriasis for at least two decades. Only five patients had prior exposure to biologic therapy, four with ustekinumab and one with risankizumab, while 25 were biologic-naïve. Half had previously tried apremilast, and nearly all used concomitant topical therapy. Notably, no patients discontinued treatment before week 28 among those included in the analysis.

The effectiveness data tell a story of rapid improvement followed by sustained consolidation. The mean PASI score fell from 11.45 at baseline, with a median of 9.2, to 7.79 at week 4, 4.69 at week 16, 3.71 at week 28, 3.53 at week 40, and 2.90 at week 52. The steepest decline occurred in the early treatment phase, particularly by week 16, after which scores continued to drift downward or held steady through the maintenance phase. This pattern suggests that tildrakizumab induces a rapid initial response that is then maintained with continued dosing in routine clinical practice, exactly the profile clinicians hope for in a disease requiring lifelong management.

Responder analyses added a crucial layer of rigor. The researchers applied non-responder imputation (NRI), a conservative method in which patients who discontinued treatment or had missing PASI data are classified as non-responders at subsequent visits. Under this approach, PASI75 achievement, meaning a 75 percent reduction in disease severity, rose from 3.3 percent at week 4 to 36.7 percent at week 16, 46.7 percent at week 28, 50.0 percent at week 40, and 56.7 percent at week 52. Absolute disease control, defined as a PASI score of 3 or less, followed a similar trajectory, reaching 60.0 percent at week 52 with a 95 percent confidence interval of 42.3 to 75.4. As-observed rates, which count only evaluable patients, were higher still, at 68.0 percent for PASI75 and 72.0 percent for PASI ≤3 at week 52.

Four patients stopped treatment because of insufficient efficacy, with final PASI scores of 7.5 at week 4, 1.6 at week 16, 3.7 at week 28, and 3.2 at week 40; two subsequently switched to another biologic and two returned to conventional systemic or topical therapy. The remaining 26 patients, or 86.7 percent of the cohort, continued treatment through week 52. Safety was assessed retrospectively from electronic medical records rather than through protocolized surveillance, a limitation the authors acknowledge candidly. Seven adverse events were documented, including low back pain associated with spinal canal stenosis, injection-site erythema, facial erythema, pruritus, hyperlipidemia, chest tightness, and vesicular eruptions on the hands and feet, one event each. Critically, no treatment discontinuations related to adverse events occurred.

How do these numbers compare with European real-world studies? The picture is heterogeneous, and the authors argue the discrepancies are more plausibly attributable to methodology than to true differences in drug performance. The Italian IL-PSO multicenter retrospective study reported PASI75 rates approaching 90 percent at week 52, while a German retrospective multicenter analysis over 76 weeks reported PASI75 in 85.5 percent and absolute PASI below 3 in 79.7 percent. A large Basque Country cohort of 212 patients reported PASI75 in 66.4 percent and PASI ≤3 in 68.8 percent. The Iwate cohort’s lower PASI75 rate likely reflects its relatively low baseline mean PASI of 11.45, compared with 16.0 in the German TILOT study and 14.45 in IL-PSO, combined with the conservative NRI approach. In cohorts with lower baseline severity, relative thresholds like PASI75 are mathematically harder to reach, whereas absolute measures such as PASI ≤3 may better capture meaningful disease control.

The exploratory subgroup analyses yielded one intriguing signal. At week 52, non-smokers showed a numerically higher PASI ≤3 achievement rate than current or former smokers, 88.9 percent versus 47.6 percent, an association that reached nominal significance in unadjusted analysis with a p value of 0.049 but dissolved after Holm adjustment for multiple comparisons across 20 subgroup tests, yielding an adjusted p value of 0.984. No other baseline factors, including sex, body mass index, age, or disease duration, showed significant differences. The authors frame the smoking finding as hypothesis-generating, noting that smoking has been reported to adversely affect biologic treatment response in psoriasis, and they emphasize that the retrospective single-center design, small sample size, and lack of confounder adjustment demand caution. Older patients aged 65 and above responded comparably, consistent with prior real-world studies of tildrakizumab in elderly populations. Taken together, the study bridges Japanese trial data and everyday practice, suggesting that for many patients the realistic therapeutic goal is not dramatic relative improvement but stable, low absolute disease activity sustained over the long haul.

Subject of Research: Real-world effectiveness and safety of the interleukin-23 p19 inhibitor tildrakizumab in Japanese patients with plaque psoriasis over 52 weeks

Article Title: Real-world effectiveness and safety of tildrakizumab in Japanese patients with psoriasis: a single-center 52-week observational study

Article References: Watabe, D., Tsunoda, K., Hamabata, A., Goto, M., Yoshioka, W., & Amano, H. (2026). Real-world effectiveness and safety of tildrakizumab in Japanese patients with psoriasis: a single-center 52-week observational study. Journal of Cutaneous Immunology and Allergy, 9, Article 16442. https://doi.org/10.3389/jcia.2026.16442

Image Credits: AI Generated

DOI: 10.3389/jcia.2026.16442

Keywords: tildrakizumab, psoriasis, interleukin-23, real-world evidence, biologic therapy, PASI, Japan, dermatology, Th17 axis, drug safety, observational study, immunology

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