Long COVID, also known as post-acute sequelae of COVID-19 or PASC, affects people who continue to experience symptoms weeks or months after the initial infection. Estimates vary across studies, but neurological complaints are among the most frequently reported. Patients describe “brain fog,” difficulties with attention and memory, chronic fatigue, headaches, burning or prickling sensations, muscle and joint pain, and abnormal sensitivity to pressure or temperature. The causes remain uncertain. Proposed explanations include persistent viral material, abnormal immune activation, vascular dysfunction, reactivation of latent viruses, and damage to the nervous system. Autoimmunity—the mistaken targeting of the body’s own proteins by immune defenses—has become one of the leading hypotheses, although no single long-COVID autoantibody has yet been consistently identified.

To test whether antibodies might actively contribute to symptoms, researchers in Belgium recruited 13 adults with long COVID and neurological complaints and compared them with 10 age- and sex-matched individuals without persistent symptoms. The long-COVID participants had been infected with SARS-CoV-2 an average of roughly three years before enrollment. All reported pain, fatigue, and cognitive difficulties, while a substantial proportion met questionnaire-based criteria for neuropathic pain. The participants underwent detailed neuropsychological testing, including assessments of memory, attention, executive function, anxiety, depression, and pain. People with previous neurological or autoimmune disorders were excluded, reducing the possibility that the antibody findings were caused by an unrelated pre-existing disease.

The investigators isolated immunoglobulin G, or IgG, from the participants’ blood using protein G purification. IgG is the most abundant antibody class in human circulation and normally helps identify and neutralize pathogens. In autoimmune disease, however, some IgG molecules can bind to self-antigens and alter the behavior of cells, activate immune receptors, or promote tissue injury. The purified antibodies were injected into female C57BL/6J mice at a dose of 8 milligrams per day for four consecutive days. Each human antibody preparation was administered to a separate group of animals, allowing the researchers to compare the effects of antibodies from long-COVID patients with those from healthy controls. The mice were then monitored for two weeks using behavioral tests designed to measure pain sensitivity, memory, anxiety, depressive-like behavior, and general well-being.

The clearest effect appeared in tests of sensory sensitivity. Mice receiving IgG from long-COVID patients withdrew their paws more rapidly from a radiant heat stimulus in the Hargreaves test, indicating thermal hypersensitivity. They also responded to weaker mechanical stimulation in the Von Frey test, a standard assay for mechanical allodynia—the experience of normally harmless touch as painful. These changes were strongest during the first several days after antibody administration and faded during the following week. A facial-grimace assessment, used as an indirect measure of discomfort in laboratory mice, also showed a temporary increase in abnormal facial expressions on the first day. Not every pain assay produced the same result: the hot-plate test did not reveal a significant difference between the groups, illustrating how distinct experimental measures can capture different aspects of nociception.

Additional experiments strengthened the argument that the pain-like responses were caused by intact IgG rather than by another component of the blood preparation. When the researchers injected serum from which IgG had been removed, the hypersensitivity was largely abolished. The same occurred after the antibodies were treated with papain, an enzyme that cuts IgG molecules into antigen-binding Fab fragments and an Fc fragment. Although the digestion was incomplete, the treated material no longer produced the same behavioral effects as native purified IgG. The result suggests that the structural integrity of the antibody is important for the response, although it does not by itself reveal whether the critical activity depends on antigen binding, Fc-receptor signaling, or a combination of both.

Microscopic analysis provided a possible anatomical explanation. Human IgG from long-COVID patients accumulated in the lumbar dorsal root ganglia, clusters of sensory-neuron cell bodies located outside the spinal cord. These structures are unusually accessible to circulating molecules because they contain fenestrated blood vessels, which are more permeable than the vessels that normally protect the brain. In mice given patient-derived IgG, the human antibodies were detected directly on sensory neurons and overlapped with the neuronal marker NeuN. They did not substantially colocalize with satellite glial cells, the support cells that surround sensory neurons. The antibodies appeared to recognize several neuronal populations, including neurons marked by NF200 and, to a lesser extent, peripherin and calcitonin gene-related peptide. These markers broadly represent large myelinated fibers involved in mechanosensation and proprioception, as well as smaller fibers involved in pain and temperature detection.

The researchers also tested whether the antibodies could bind human nervous tissue. When purified IgG was applied to post-mortem human dorsal root ganglia, samples from long-COVID patients showed more punctate staining on sensory-neuron cell bodies than samples from healthy controls. Antibodies from both groups could bind satellite glial cells, but the neuron-associated pattern was more prominent in the long-COVID preparations. The punctate appearance may reflect antibodies attaching to clusters of membrane proteins, ion channels, or receptors, although the precise target remains unknown. A commercial microarray containing 120 neurological and brain-associated antigens failed to identify a common autoreactivity profile. The result does not rule out autoimmunity: conformational epitopes, which depend on a protein’s three-dimensional structure, can be destroyed or hidden when antigens are immobilized on an array. The study therefore leaves open the possibility that the relevant targets are unusual, intracellular, or structurally dependent proteins.

The absence of central nervous system effects was equally important. Human IgG was not detected in the brain parenchyma or spinal cord, apart from antibody staining in vascular or connective tissues such as the meninges and choroid plexus. Mice that received long-COVID IgG performed similarly to control animals in Barnes-maze and Y-maze tasks assessing spatial memory and working memory. They also showed no meaningful differences in elevated-plus-maze or light-dark-box tests of anxiety, or in the tail-suspension test used to measure depressive-like behavior. Locomotor activity and nest-building behavior were unchanged. Examination of the brain, spinal cord, and dorsal root ganglia found no clear increase in microglia or astrocytes, and gene-expression analyses detected no significant rise in the inflammatory markers Iba1 or Gfap. These observations suggest that the transferred antibodies produced a functional change in sensory signaling without triggering widespread neuroinflammation.

The findings do not establish that all long-COVID pain is autoimmune, nor do they show that antibodies cause brain fog or other cognitive symptoms in patients. The study involved only 13 affected participants, most of them women, and relied on a short-term, high-dose passive-transfer model in female mice. Human antibodies may recognize mouse proteins differently from human proteins, and human IgG does not necessarily interact with mouse immune receptors in the same way it does with human receptors. The researchers also measured behavior for only two weeks, whereas long COVID can persist for years. Nevertheless, the work offers a mechanistic bridge between patient blood samples and pain-related biology: IgG from a carefully selected neurological long-COVID cohort bound sensory neurons and temporarily induced hypersensitivity in animals, while antibody depletion or enzymatic disruption prevented the effect. Identifying the responsible antibody targets will be the next major challenge. Future studies using unbiased antibody profiling, cultured human sensory neurons, electrophysiology, and cell-based assays may determine whether these antibodies alter ion-channel activity, activate neuronal Fc receptors, or interfere with signaling pathways that regulate nociception. If confirmed in larger cohorts, the results could help define an immune-mediated subtype of long-COVID pain and guide treatments aimed at neutralizing or removing pathogenic antibodies.

Subject of Research: The potential role of IgG autoantibodies in neurological long COVID, particularly pain-related sensory dysfunction.

Article Title: Pathogenic IgG from long COVID patients with neurological sequelae triggers sensitive but not cognitive impairments upon transfer into mice

Article References: Mignolet M, Deroux C, Florkin T, et al. “Pathogenic IgG from long COVID patients with neurological sequelae triggers sensitive but not cognitive impairments upon transfer into mice.” Acta Neuropathologica 151, article 50 (2026).

Image Credits: AI Generated

DOI: 10.1007/s00401-026-03019-0

Keywords: Long COVID; SARS-CoV-2; post-acute sequelae of COVID; IgG antibodies; autoimmunity; neuropathic pain; mechanical allodynia; thermal hypersensitivity; dorsal root ganglia; sensory neurons; neuroimmunology; passive antibody transfer

The researchers examined how the LRRK2 G2019S mutation influences neutrophils, which are part of the innate immune system. Unlike adaptive immune cells, which learn to recognize specific pathogens over time, neutrophils respond rapidly to signs of infection. They migrate through the bloodstream toward damaged or infected tissue, engulf bacteria in a process called phagocytosis and expose the captured microbes to a range of destructive mechanisms. One of the most important is the production of reactive oxygen species, or ROS. These chemically reactive molecules can damage bacterial membranes, proteins and DNA after microbes have been enclosed inside a neutrophil. The new study found that neutrophils carrying the Parkinson’s-linked mutation generated substantially higher levels of ROS, giving them a greater capacity to eliminate bacteria living inside immune cells.

The researchers traced this effect to NADPH oxidase 2, an enzyme complex that acts as a molecular generator of reactive oxygen species. When activated, NADPH oxidase 2 transfers electrons to oxygen, producing molecules such as superoxide that can be converted into other antimicrobial oxidants. This oxidative burst is a central weapon used by neutrophils against engulfed bacteria. The G2019S form of LRRK2 appears to increase the activity of this system, effectively amplifying the oxidative response after a neutrophil encounters a pathogen. The result is not simply a higher level of immune-cell activation, but a specific biochemical change that improves the cells’ ability to create the hostile chemical environment required to kill intracellular bacteria. This mechanistic link helps explain why the mutation enhanced bacterial control in the experimental models.

To test the consequences of the mutation during infection, the team studied Salmonella Typhimurium, a bacterium capable of invading cells and causing serious disease. Salmonella can survive inside host cells by manipulating cellular processes that would normally destroy it. The researchers found that the pathogen produces a protein that suppresses the generation of reactive oxygen species, weakening one of the neutrophil’s most important antimicrobial defenses. By reducing the oxidative burst, Salmonella can improve its chances of remaining alive inside immune cells and may gain additional time to spread. Neutrophils carrying the LRRK2 mutation countered this strategy more effectively, producing stronger ROS responses and demonstrating superior control of the intracellular bacteria. The results reveal a direct molecular contest between a pathogen attempting to silence an immune defense and host cells equipped to intensify it.

This interaction illustrates what scientists often describe as an evolutionary arms race. Bacteria evolve proteins and secretion systems that interfere with immune signaling, alter cellular trafficking or neutralize toxic compounds. Hosts, in turn, develop genetic and biochemical mechanisms that detect infection and restore the ability to destroy invading organisms. A mutation that increases antibacterial activity could, under some circumstances, provide an advantage to individuals exposed to recurrent or severe infections. The researchers suggest that the persistence of LRRK2 variants in human populations may partly reflect this kind of evolutionary pressure, although the study does not establish that infection alone selected the mutation. Instead, the findings provide a plausible biological framework for understanding why a variant that can contribute to neurological disease might also influence host defense.

The apparent benefit comes with an important warning. Reactive oxygen species are powerful but indiscriminate molecules. They can damage pathogens, yet excessive or prolonged oxidative activity can injure healthy proteins, membranes and surrounding tissues. Neutrophils are essential for controlling acute infections, but their activation can also contribute to chronic inflammatory disorders when the response does not switch off appropriately. LRRK2 mutations have been associated with inflammatory conditions including Crohn’s disease and leprosy, although the precise role of the gene in these diseases remains unresolved. The new results suggest that increased LRRK2 activity could help explain how an immune response becomes more effective against bacteria while simultaneously increasing the risk of collateral tissue damage. In biological terms, the mutation may sharpen the immune system’s weapon without necessarily improving its ability to control when that weapon is used.

The findings may also contribute to a broader understanding of Parkinson’s disease. The G2019S mutation increases the kinase activity of LRRK2, an enzyme that modifies other proteins by adding phosphate groups. In neurons, altered LRRK2 signaling has been linked to cellular pathways involved in vesicle trafficking, organelle function and neurodegeneration. The new work shows that the same mutation can alter the behavior of neutrophils through NADPH oxidase 2 and oxidative metabolism. This raises the possibility that immune changes associated with LRRK2 could influence the environment in which neurodegenerative disease develops. Infections and inflammation can affect the brain through circulating immune signals, changes in the blood-brain barrier and activation of brain-resident immune cells. The study does not prove that bacterial infections cause Parkinson’s disease or that enhanced neutrophil activity directly damages neurons, but it provides a reason to investigate how peripheral immune responses may contribute to long-term changes in vulnerable brain regions.

The therapeutic implications are potentially significant, although they remain at an early research stage. Current strategies aimed at LRRK2 often focus on reducing its activity because excessive signaling has been implicated in Parkinson’s disease and other disorders. The new findings indicate that indiscriminate suppression could also weaken an important antibacterial pathway. A future treatment might therefore need to modulate LRRK2 with much greater precision, limiting harmful signaling in specific tissues while preserving or carefully adjusting its function in immune cells. Similar approaches could be used to regulate NADPH oxidase 2 or the oxidative burst itself. The objective would not be to simply turn immunity up or down, but to maintain enough ROS production to eliminate microbes while preventing the persistent oxidative stress that promotes inflammation. Such therapies would require careful testing because neutrophil function is essential for protection against a wide range of infections.

The University of Ottawa team plans to examine how other LRRK2 mutations affect immune responses and disease progression. Different genetic variants may alter the protein in distinct ways, producing immune effects that cannot be predicted from the G2019S mutation alone. Future research may also investigate whether repeated infections create lasting changes in the brain or immune system of people carrying LRRK2 variants. For now, the study presents a striking example of how a gene associated with one disease can influence an entirely different biological system. By showing that the Parkinson’s-linked mutation increases NADPH oxidase 2 activity in neutrophils and improves control of intracellular Salmonella, the research connects neurodegeneration, innate immunity and microbial survival in a single molecular story. It also reinforces a central principle of immunology: the strongest defense is not always the safest one, and health depends on keeping both sides of that equation in balance.

Subject of Research: Animals

Article Title: The Parkinson’s disease-linked G2019S mutation of LRRK2 increases NADPH oxidase-2 activity in neutrophils for superior control of bacterial infections

Web References: https://www.uottawa.ca/faculty-medicine/ ; https://www.nature.com/articles/s41423-026-01451-6

References: Cellular and Molecular Immunology, DOI: 10.1038/s41423-026-01451-6

Image Credits: Faculty of Medicine, University of Ottawa

Keywords: LRRK2, G2019S mutation, Parkinson’s disease, neutrophils, innate immunity, reactive oxygen species, NADPH oxidase 2, bacterial infections, Salmonella Typhimurium, inflammation

Le Belle, J., Condro, M.C., Cepeda, C. et al. Acute rapamycin treatment reveals distinct mechanisms of dysfunction in a maternal inflammation mouse model.
Nat Commun 17, 6386 (2026). https://doi.org/10.1038/s41467-026-74958-1

https://doi.org/10.1038/s41467-026-74958-1

Instead of treating microbiome differences as mere biomarkers, the authors synthesize evidence for biological pathways that plausibly transmit signals from the gut to the nervous system. They focus on how microbial communities can influence neuroactive chemistry, immune activity, and stress-response circuits that are often implicated in mental health.

One highlighted mechanism involves microbial metabolites—small molecules produced during fermentation and nutrient processing. These compounds can interact with host signaling systems, including pathways that regulate inflammation and neuronal signaling. By altering metabolite profiles, changes in gut ecology may shift the chemical environment that the brain indirectly receives.

Immune modulation is another central theme. The gut hosts a large fraction of the body’s immune cells, and microbial cues can shape cytokine production and immune tone. The study emphasizes that inflammatory signals can reach the brain through multiple routes, potentially affecting synaptic plasticity and neurotransmission.

The paper also discusses the gut barrier and microbial translocation risk. When intestinal permeability increases, bacterial components may access systemic circulation more readily, activating inflammatory pathways and potentially intensifying neuropsychiatric symptoms.

Stress physiology may connect these processes as well. The authors describe how stress hormones can alter gut microbial composition, which in turn can feed back to influence stress-reactive pathways. This bidirectional relationship supports a cycle in which microbial imbalance and mental symptoms reinforce each other.

Crucially, the authors frame causality as something that must be tested with mechanistic experiments, not inferred solely from observational studies. They outline experimental strategies that can strengthen causal inference, such as targeted manipulation of microbial taxa or metabolites and downstream measurement of brain-relevant outcomes.

Overall, the work positions the microbiome as a dynamic, bioactive system rather than a passive indicator. If verified in longitudinal and intervention studies, the proposed pathways could inform microbiome-based diagnostics and therapeutic approaches for psychiatric disorders.

Subject of Research: Gut microbiome mechanisms in psychiatric disorders
Article Title: From association to causality: mechanistic pathways linking the gut microbiome to psychiatric disorders.
Article References: Almarzooqi, S., Yassin, L.K., Alnuaimi, F. et al. From association to causality: mechanistic pathways linking the gut microbiome to psychiatric disorders. Transl Psychiatry (2026). https://doi.org/10.1038/s41398-026-04305-x
DOI: https://doi.org/10.1038/s41398-026-04305-x
Image Credits: AI Generated

For decades, antidepressants have been conceptualized primarily through their ability to rebalance neurotransmitters such as serotonin, norepinephrine, and dopamine. However, accumulating clinical and experimental data have challenged this narrow framework, revealing that immune dysregulation and chronic inflammation frequently co-occur with mood disorders, particularly major depressive disorder (MDD). The study by Nava and colleagues compellingly demonstrates that antidepressants exert their effects, at least in part, by modulating cytokine networks within the central nervous system, orchestrating an immunological milieu conducive to mood stabilization.

At the heart of this work lies the comprehensive profiling of cytokines—small signaling proteins that mediate immune responses—in neuronal and glial populations under the influence of various classes of antidepressants. The research utilized cutting-edge multiplex assays and single-cell RNA sequencing to dissect cytokine expression patterns with extraordinary resolution. Results indicate that selective serotonin reuptake inhibitors (SSRIs), tricyclic antidepressants (TCAs), and novel agents variably downregulate pro-inflammatory cytokines such as interleukin-1 beta (IL-1β), tumor necrosis factor-alpha (TNF-α), and interferon-gamma (IFN-γ), while concurrently upregulating anti-inflammatory mediators like interleukin-10 (IL-10) and transforming growth factor-beta (TGF-β). This bidirectional modulation appears critical for re-establishing homeostatic neuroimmune conditions that support emotional resilience.

A particularly intriguing finding involves the differential regulation of microglial activation states. Microglia, the resident immune cells of the brain, dynamically shift between pro-inflammatory (M1) and anti-inflammatory (M2) phenotypes. Nava et al. reveal that antidepressants promote a phenotypic shift towards M2-like states, characterized by enhanced phagocytic activity, trophic support for neurons, and secretion of neuroprotective cytokines. This microglial reprogramming likely attenuates chronic neuroinflammation implicated in synaptic remodeling deficits and anhedonia, common hallmarks of depression. The study’s data resonate with emerging theories positioning microglial plasticity as a therapeutic target.

Beyond microglia, astrocytes and neurons themselves emerge as critical sources and targets of cytokine modulation. The study illuminated complex autocrine and paracrine feedback loops whereby astrocytes respond to antidepressant exposure by secreting neuroimmune factors that alter synaptic function and plasticity. Concretely, changes in chemokine gradients and growth factor production directly influenced neural circuits implicated in mood regulation, including the hippocampus, prefrontal cortex, and amygdala. These insights broaden the classical neurochemical view and spotlight glial-neuronal crosstalk as integral to antidepressant action.

Additionally, the work tackles the temporal dimension of cytokine modulation, revealing that neuroimmune changes precede mood improvements in both animal models and clinical observations. This temporal precedence underscores cytokine networks as potential biomarker candidates for treatment response, offering new diagnostic tools for clinicians. Advances in peripheral and cerebrospinal fluid cytokine profiling could soon allow personalized medicine approaches, tailoring antidepressant regimens based on individual immune signatures to maximize therapeutic efficacy while minimizing adverse effects.

Importantly, the mathematical modeling components in Nava et al.’s study provide a sophisticated framework for understanding the nonlinear dynamics of cytokine interactions. By simulating feedback loops and cytokine network topology alterations induced by antidepressants, the authors propose mechanistic hypotheses that reconcile variability in clinical treatment outcomes with underlying immunological heterogeneity. This integrative model could inform future clinical trial designs, stratifying patients by cytokine network profiles to optimize intervention strategies.

Of particular relevance from a translational perspective is the study’s exploration of novel pharmacological agents that target cytokine pathways directly. Compounds inhibiting the NLRP3 inflammasome, a core regulator of IL-1β maturation, showed synergistic effects when combined with traditional antidepressants in animal behavioral paradigms. These findings pave the way for adjunct immunomodulatory therapies explicitly designed to rectify aberrant neuroimmune states associated with mood dysregulation, heralding a new era of combinatorial treatments for depression resistant to conventional approaches.

The implications for neuropsychiatric disorders extend far beyond depression. Given the neuroimmune basis for comorbidities observed in anxiety disorders, bipolar disorder, and schizophrenia, insights gleaned from this research may catalyze paradigm shifts in understanding diverse psychopathologies. By elucidating the bidirectional couplings between emotional states and immune function, the study highlights the potential of immunopsychiatry as a transformative discipline bridging neurology, psychiatry, and immunology.

Moreover, this research invigorates public health approaches to managing mood disorders. Recognizing the immune dimension of depression invites integrative treatment modalities incorporating diet, exercise, and stress reduction techniques known to impact systemic inflammation. Consequently, therapeutic strategies extending beyond pharmacology emerge as viable complements to neuroimmune modulation, promising holistic benefits to patients.

Beyond its clinical relevance, the methodological rigor and interdisciplinary synthesis in Nava et al.’s work set a new benchmark for neuropsychiatric research. The seamless integration of immunology, molecular biology, computational modeling, and behavioral neuroscience exemplifies a modern approach to unraveling complex brain disorders. The study’s design anticipates future advances in single-cell and spatial transcriptomics that will further clarify cell-type specific cytokine contributions in human brains.

In conclusion, this landmark study redefines the landscape of antidepressant research by illuminating the critical role of neuroimmune cytokine networks in mood regulation. By elucidating how diverse classes of antidepressants orchestrate cytokine signaling to recalibrate brain-immune dialog, Nava and colleagues provide a mechanistic blueprint underpinning emotional resilience. These insights not only enhance our biological understanding of depression but also inspire innovative therapeutic paradigms that harness neuroimmune plasticity. As research momentum accelerates, the nexus of psychiatry and immunology promises to yield revolutionary breakthroughs in preventing and treating mood disorders.

Subject of Research: Neuroimmune regulation of mood disorders; modulation of cytokine networks by antidepressants

Article Title: Modulation of neuroimmune cytokine networks by antidepressants: implications in mood regulation

Article References:
Nava, R.G., Adri, A.S., Filgueiras, I.S. et al. Modulation of neuroimmune cytokine networks by antidepressants: implications in mood regulation. Transl Psychiatry 15, 314 (2025). https://doi.org/10.1038/s41398-025-03532-y

Image Credits: AI Generated

DOI: https://doi.org/10.1038/s41398-025-03532-y

Sepsis-associated encephalopathy represents a diffuse cerebral dysfunction triggered by systemic infection and inflammation, characterized by delirium, cognitive deficits, and long-term neurological impairment. Central to this pathology is an overactive immune response that compromises the delicate homeostasis of the central nervous system (CNS). Microglia, the brain-resident macrophages, orchestrate the neuroimmune response, modulating inflammation, clearing cellular debris, and maintaining neural circuitry integrity. Among microglial phenotypes, the alternatively activated M2 type is associated with anti-inflammatory and reparative functions. Understanding how these microglia coordinate efferocytosis—the process of engulfing and removing apoptotic cells—has remained a critical gap until now.

The researchers focused on the GAS6 (growth arrest-specific 6) protein and its receptor, AXL, a receptor tyrosine kinase belonging to the TAM family, known to regulate immune homeostasis and cell clearance. Prior studies had hinted at the GAS6/AXL axis’s involvement in diverse inflammatory settings, but its precise role within the CNS microenvironment during sepsis remained elusive. Through a combination of in vivo and in vitro experiments utilizing murine models of sepsis and primary microglial cultures, the study delineated how GAS6 binding to AXL on M2 microglia dramatically enhanced their efferocytic capacity.

Mechanistically, activation of AXL triggered downstream signaling cascades, including the PI3K/Akt and ERK pathways, which are vital for cytoskeletal remodeling and phagosome formation. These intracellular events facilitated the efficient recognition, engulfment, and degradation of apoptotic neurons and cellular debris resulting from sepsis-induced brain injury. Notably, inhibiting the GAS6/AXL axis suppressed efferocytosis, exacerbating neuroinflammation and neurodegeneration, thereby underscoring its protective role. This phenomenon was accompanied by a reduction in pro-inflammatory cytokines such as IL-1β and TNF-α and an increase in anti-inflammatory mediators like IL-10, indicating a balanced immune milieu fostered by GAS6/AXL signaling.

One of the notable strengths of this work lies in its detailed dissection of microglial polarization dynamics. By leveraging flow cytometry, immunohistochemistry, and gene expression analyses, the investigators demonstrated that the GAS6/AXL pathway preferentially enhanced M2 microglial phenotypes while dampening pro-inflammatory M1 characteristics. This shift was crucial in containing the deleterious effects of systemic inflammation on brain tissue. Furthermore, the study revealed temporal nuances where GAS6/AXL activation was most pronounced during the acute phases of sepsis, highlighting a window of opportunity for therapeutic intervention.

In addition to advancing molecular understanding, the researchers explored translational potential by administering recombinant GAS6 protein to septic animal models. Treatment not only augmented microglial efferocytosis but also significantly improved neurological outcomes, measured through behavioral assays assessing motor coordination and cognitive functions. These promising results set a precedent for future clinical trials aimed at harnessing GAS6/AXL signaling to treat SAE patients.

Sepsis-associated encephalopathy remains poorly understood, partly due to the complexity of immune-brain interactions and the heterogeneity of patient presentations. This study’s comprehensive approach combining molecular biology, neuroimmunology, and in vivo modeling offers a robust framework to unravel these complexities. The identification of GAS6/AXL as a key regulator of neuroprotective microglial functions presents a paradigm shift, moving beyond systemic infection control toward targeted modulation of CNS immunity.

The implications of these findings extend beyond sepsis, potentially influencing therapeutic strategies for other neuroinflammatory disorders such as Alzheimer’s disease, multiple sclerosis, and traumatic brain injury, where aberrant microglial activation plays a detrimental role. By restoring efferocytosis and fostering tissue repair, manipulation of the GAS6/AXL pathway could represent a universal mechanism to modulate CNS inflammation safely.

Importantly, the study carefully considered the safety profile of manipulating GAS6/AXL signaling. Given AXL’s involvement in cancer progression and immune evasion in tumors, the authors emphasize the need for precise targeting and timing in potential therapies to avoid unintended oncogenic effects. Nonetheless, the CNS-specific delivery and localized activation strategies could mitigate such risks, making GAS6/AXL modulation a viable therapeutic target with minimal systemic adverse effects.

This research also paves the way for biomarker development. Elevated levels of GAS6 or soluble AXL in cerebrospinal fluid or blood could serve as diagnostic indicators for the severity of SAE or treatment efficacy. Such biomarkers would be invaluable in the clinical setting for patient stratification, prognosis, and monitoring therapeutic responses in real time.

In conclusion, the elucidation of the GAS6/AXL signaling axis as a promoter of M2 microglial efferocytosis marks a significant advance in understanding neuroimmune crosstalk during sepsis-associated encephalopathy. By harnessing this pathway, future therapies may significantly reduce the burden of cognitive impairment and mortality associated with sepsis-related brain dysfunction. Continued research into the molecular intricacies and translational applications of this pathway will undoubtedly reshape approaches to managing sepsis and other devastating neuroinflammatory conditions.

As the scientific community strives to combat the global burden of sepsis and its neurological complications, discoveries such as these offer hope for novel, mechanism-based interventions that enhance the body’s innate ability to heal the brain. The GAS6/AXL axis stands out as a beacon in this landscape, illuminating new frontiers in neuroimmunology and clinical neuroscience.

Subject of Research: GAS6/AXL signaling and its role in promoting M2 microglial efferocytosis to alleviate neuroinflammation in sepsis-associated encephalopathy.

Article Title: GAS6/AXL signaling promotes M2 microglia efferocytosis to alleviate neuroinflammation in sepsis-associated encephalopathy.

Article References: Tang, Y., Hu, H., Xie, Q. et al. GAS6/AXL signaling promotes M2 microglia efferocytosis to alleviate neuroinflammation in sepsis-associated encephalopathy. Cell Death Discov. 11, 268 (2025). https://doi.org/10.1038/s41420-025-02507-8

Image Credits: AI Generated

DOI: https://doi.org/10.1038/s41420-025-02507-8