Gut Epithelial Cells Could Be the Hidden Origin of Multiple Sclerosis

Multiple sclerosis has been treated as a brain and spinal cord disease for most of its medical history, with therapies aimed squarely at the central nervous system. A new study published in Science Immunology now challenges that frame, presenting early but detailed evidence that the gut, specifically the lining of the small intestine, may be where the immune attack originates. If the findings hold up in broader clinical research, they could redirect how the disease is both understood and treated.

How Intestinal Cells Prime Pathogenic T Cells in MS

Under normal conditions, intestinal epithelial cells, the single-cell layer lining the gut, do not present antigens to immune cells. That job belongs to specialized antigen-presenting cells elsewhere in the immune system. In both a mouse model of MS and in tissue from human MS patients, the researchers found something unexpected: intestinal epithelial cells were abnormally expressing major histocompatibility complex class II, or MHC II, a molecular machinery that allows cells to display protein fragments to CD4+ T cells.

The expression was especially prominent in the ileum, the final stretch of the small intestine. Using that MHC II display, the epithelial cells were presenting antigens to CD4+ T cells and pushing them toward a pathogenic subtype called Th17. Th17 cells are known drivers of autoimmune inflammation; in the context of MS, they are the immune actors that infiltrate the central nervous system and attack myelin, the protective sheath around nerve fibers.

To confirm that this process was causal rather than coincidental, the researchers conditionally deleted MHC II specifically from intestinal epithelial cells in mice. The result was a reduction in pathogenic Th17 cell generation and measurably lower disease severity in the experimental autoimmune encephalomyelitis, or EAE, model used to study MS. Functional coculture experiments using intestinal organoids and the myelin oligodendrocyte glycoprotein antigen further confirmed that MHC II-dependent antigen presentation by epithelial cells could drive the differentiation of the inflammatory T cell subset.

The Gut-to-Spinal-Cord Migration at the Heart of the Theory

Nearly 2.8 million people worldwide live with MS, a number that has risen across every world region since 2013. For most of them, existing therapies focus on dampening immune activity in the central nervous system or targeting B cells. The new findings, if they translate to clinical treatments, would shift the therapeutic window much earlier in the disease process, to the gut, before pathogenic T cells ever reach the brain or spinal cord.

The study tracked where the gut-primed Th17 cells went after activation. Using parabiosis experiments and a photoconversion model involving Kaede protein transgenic mice, which allow specific cell populations to be color-labeled and followed, the team traced Th17 cells from the intestinal lamina propria, the connective tissue layer beneath the epithelium, to the spinal cord. This gut-to-CNS migration appears to be a key step in driving neuroinflammation. As Dr. Tomohisa Sujino noted in describing the team's motivation: "Increasing evidence shows that the gut microbiota influences neurological diseases such as Parkinson's, Alzheimer's, and MS. However, the mechanisms linking gut microbes, intestinal immunity, and brain inflammation remain unclear."

The migration data, combined with the single-cell RNA sequencing performed on intestinal biopsies from both EAE mice and MS patients, suggests a conserved gut-CNS axis operating in both species, not merely a mouse-model artifact.

What Made This Study Methodologically Credible

Several methodological choices strengthened the causal claims. Single-cell RNA sequencing on intestinal biopsies allowed the team to examine antigen presentation pathways and Th17 accumulation at cellular resolution, comparing disease and healthy states. The conditional deletion of epithelial MHC II was targeted enough to isolate the contribution of gut epithelial cells without disrupting the broader immune landscape. And the organoid coculture experiments provided a controlled in vitro environment to test whether epithelial antigen presentation alone was sufficient to initiate pathogenic T cell differentiation.

The convergence across mouse models and human patient tissue is notable. Research into how gut microbiota dysbiosis affects T cell balance in MS has accumulated steadily over the past decade, but identifying a specific cellular mechanism, epithelial MHC II expression as the initiating step, is a more precise claim than the field has been able to make before.

Open Questions About Microbiome Triggers and Human Relevance

The researchers are candid that the precise mechanisms linking gut microbes to the immune cells that ultimately attack the central nervous system remain to be fully elucidated. What causes intestinal epithelial cells to upregulate MHC II in the first place? Whether specific microbial species or microbial metabolites are responsible, and whether those triggers differ between patients, is not yet answered by this study.

A broader body of work on the gut-brain axis and MS mechanisms has proposed that a leaky gut, altered microbial composition, and dysregulated immune signaling all contribute to MS risk and progression, but the interactions between these factors are still being mapped. The current study identifies a cellular actor, the antigen-presenting epithelial cell, but does not fully explain what instructs it to behave pathogenically.

It is also worth noting that EAE, while the standard preclinical model for MS research, does not capture the full heterogeneity of MS in humans. The disease presents differently across patients, and whether epithelial MHC II upregulation is a universal feature of human MS or a feature of certain subtypes will require larger, more diverse patient cohorts.

Gut-Targeted Therapies as the Next Frontier for MS Research

Despite those open questions, the therapeutic implications are generating interest. Dr. Shohei Suzuki put it directly: "While current therapies for MS often target B cells, our study highlights the gut as an important therapeutic site. Modulating intestinal microbiota or antigen-presenting activity of IECs represents new approaches to treating autoimmune neurological diseases."

Practically, that could mean interventions aimed at suppressing epithelial MHC II expression, altering the microbial composition of the gut to reduce the antigenic triggers, or identifying patients with elevated gut Th17 activity before neurological symptoms appear. Researchers at the University of Vermont and elsewhere are already working on predictive models and biomarkers from the gut microbiome for personalized MS treatment, and this study gives that program a more defined cellular target to work with.

This is preliminary research, and the path from a mouse model finding to a licensed therapy is long. But the identification of intestinal epithelial antigen presentation as a potential initiator of neuroinflammation offers a mechanistic foothold that has been missing from the gut-MS story. For a disease affecting millions with no cure and limited disease-modifying options, that is a foothold worth following.

Evidence rating

INVESTIGATIONAL — 84/100

Caveats:

• The primary experiments were conducted in mice (EAE model); human findings are associative and have not been tested in a controlled clinical trial.
• Funding source was not disclosed in the article, so independent verification of financial interests cannot be confirmed.
• This research identifies a mechanism but does not yet establish a therapeutic target or diagnostic application in humans.
• Results have not yet been independently replicated by other research groups.

Mixed-method study combining murine EAE models (conditional knockout, parabiosis, photoconversion) with human MS patient tissue analysis and IEC organoid coculture assays. The animal data establish a mechanistic causal chain, while the human data are associative and cannot establish causation on their own. The findings have not yet been independently replicated in a separate cohort or by an external research group.

References

1. Shohei Suzuki, Kentaro Miyamoto, Anna Tojo, et al. (2026). Intestinal epithelial MHC class II induces encephalitogenic CD4 T cells and initiates central nervous system autoimmunity. Science Immunology. https://doi.org/10.1126/sciimmunol.aec1627
2. Clare Walton, Rachel King, Lindsay Rechtman, et al. (2020). Rising prevalence of multiple sclerosis worldwide: Insights from the Atlas of MS, third edition. Multiple Sclerosis Journal. https://doi.org/10.1177/1352458520970841
3. Mohammad Hosein Nemati, Esmaeil Yazdanpanah, Roya Kazemi, et al. (2025). Microbiota-Driven Mechanisms in Multiple Sclerosis: Pathogenesis, Therapeutic Strategies, and Biomarker Potential. Biology. https://doi.org/10.3390/biology14040435
4. Jingru Ren, Zhenyu Niu, Jianchun Wang, et al. (2025). The link between gut microbiota and multiple sclerosis from the perspective of barrier function. Frontiers in Immunology. https://doi.org/10.3389/fimmu.2025.1652796
5. Gut Instincts: Decoding the Microbiome's Role in Multiple Sclerosis – University of Vermont. uvm.edu. https://www.uvm.edu/news/story/gut-instincts-decoding-microbiomes-role-multiple-sclerosis