Antibody Patterns Reveal Inflammatory Bowel Disease Years Before Symptoms Appear

Scientists have uncovered evidence that the immune system begins producing telltale molecular signatures up to a decade before someone is diagnosed with inflammatory bowel disease, a discovery that could fundamentally change how the chronic condition is detected and managed. The findings, presented at UEG Week 2026 in Barcelona, come from one of the most comprehensive serological investigations ever conducted into the preclinical phase of the disease, and they suggest that the groundwork for Crohn’s disease and ulcerative colitis is laid in the body long before the first cramps, bleeding or diarrhea prompt a patient to seek medical help.

Inflammatory bowel disease is an umbrella term for a group of chronic, immune-mediated disorders of the digestive tract, the two principal forms being Crohn’s disease and ulcerative colitis. In both conditions, a dysregulated immune response drives persistent inflammation and tissue damage in the gut, producing symptoms that can be debilitating and, in many patients, lifelong. Current diagnostic practice relies largely on clinical presentation, endoscopy and imaging, all of which come into play only once disease has become symptomatic. Yet researchers have increasingly suspected that IBD does not appear out of nowhere; instead, it appears to develop over a prolonged preclinical period during which subtle biological changes accumulate. What has been missing is a detailed picture of the immune activity during that hidden window.

To build that picture, a research team led by Dr Arno Bourgonje, a Dutch physician-scientist and gastroenterologist affiliated with the University Medical Center Groningen who conducted the work during a postdoctoral fellowship at the Icahn School of Medicine at Mount Sinai in New York, turned to a remarkably rich set of biological material: serum samples collected years before diagnosis. The study analysed 2,000 serum samples from 500 individuals, comprising 200 people who went on to develop Crohn’s disease, 200 who went on to develop ulcerative colitis, and 100 age- and sex-matched healthy controls. Crucially, the samples were not drawn only at diagnosis. They had been collected at four time points: at diagnosis and approximately two, four and ten years beforehand, giving the researchers a longitudinal view of immune activity stretching back through the disease prodrome.

The technological heart of the study was massively parallel serology, an approach that allows investigators to profile antibody responses against an enormous panel of targets in a single assay. In this case, the researchers measured antibody reactivity against roughly 357,000 distinct antigens spanning microbial, viral, food-associated and immune-associated molecules. This scale matters because the immune system’s repertoire of antibodies is vast, and disease-related changes may be scattered across many different specificities rather than concentrated in a single signature. By scanning such a broad landscape, the team could capture patterns that narrower, hypothesis-driven tests would likely miss.

The sheer volume of data produced by the analysis was striking. Across the 2,000 samples, the researchers identified 123,980 unique antibodies. When they compared the participants who later developed IBD with the healthy controls, a consistent difference emerged: antibody diversity was significantly lower in people who eventually developed Crohn’s disease or ulcerative colitis. This contraction of the antibody repertoire, evident years before clinical disease, hints at an immune system already being reshaped by the pathological processes that will later manifest as gut inflammation. Distinct antibody responses were detectable in both conditions up to ten years before diagnosis.

The two diseases showed characteristically different patterns. In people who later developed Crohn’s disease, the researchers observed elevated responses against herpesviruses as well as anti-flagellin antibodies, reactivity directed against bacterial flagellin that has long been associated with immune responses in Crohn’s. These elevations were particularly pronounced in individuals who went on to develop complicated or ileal disease, the more aggressive subtypes that carry a greater burden of surgery and disability. Meanwhile, antibody responses to encapsulated bacteria progressively declined as diagnosis approached. In ulcerative colitis, the profile was different again: rising antibody responses against herpesviruses and autoantigens were accompanied by reduced reactivity to encapsulated pathogens. These divergent trajectories suggest that Crohn’s disease and ulcerative colitis may represent immunologically distinct processes already diverging during the preclinical phase.

To test whether these patterns carried real predictive power, the team integrated the early antibody signatures using machine-learning models. The results were impressive by the standards of biomarker research. The models discriminated people who would later develop Crohn’s disease or ulcerative colitis from healthy controls up to ten years before diagnosis, achieving area under the curve values of 0.90 for Crohn’s disease and 0.84 for ulcerative colitis. An AUC of 1.0 represents perfect discrimination, so values approaching 0.9 indicate strong performance. Perhaps more striking still, the profiles differentiated people who later developed complicated from non-complicated Crohn’s disease up to approximately ten years before diagnosis, with an AUC of 0.85, suggesting that the seeds of disease severity may be visible long before clinicians have any way of assessing it.

For Dr Bourgonje, one of the most intriguing aspects of the findings is what they imply about disease progression. Complicated Crohn’s disease at diagnosis was associated with a distinct antibody profile years before the first clinical symptoms, he noted, indicating that this more severe trajectory is not simply the consequence of disease progressing unchecked after diagnosis. Instead, complicated disease appears to follow a different biological course from the outset. In his view, finding these patterns so early points to the potential of antibody profiling to support earlier risk detection, distinguish between disease subtypes and help identify patients who may benefit from more intensive therapy as early as possible. That last point carries particular weight, because Crohn’s disease management increasingly favours early aggressive treatment for patients at high risk of complications, but clinicians currently lack reliable tools to identify those patients before damage accumulates.

The research builds on a growing recognition that IBD sits within a broader family of immune-mediated conditions that may have long prodromal phases, and on work illuminating the complex interplay between neutrophils, the gut microbiota and intestinal inflammation. Antibody profiling offers an attractive window onto this preclinical biology because antibodies are stable in serum, measurable at scale and reflect accumulated immune experience with microbes, viruses, food antigens and the body’s own tissues. A declining or shifting antibody repertoire in the years before diagnosis may reflect changes in mucosal immune regulation, altered interactions with the gut microbiome, or early subclinical inflammation, though the study establishes associations rather than pinpointing exact mechanisms.

The authors are careful to frame the work as a proof of principle rather than a ready-made screening tool. The samples came from a specific cohort, and before any clinical application the antibody signatures must be validated in independent, more diverse and prospectively followed populations. Beyond validation, several practical hurdles remain: researchers need to determine the added value of antibody signatures alongside genetic, clinical and other blood-based markers, translate the findings into a reproducible and affordable targeted assay, and ultimately demonstrate that using such a test actually leads to better clinical outcomes. Only then could antibody profiling move from the research bench to the clinic, where it might one day allow physicians to identify people at risk of inflammatory bowel disease years before symptoms strike, monitor which disease course they are likely to follow and intervene early enough to change that course.

Subject of Research: Preclinical immune antibody signatures preceding inflammatory bowel disease diagnosis

Article Title: Immune changes could signal inflammatory bowel disease up to 10 years before diagnosis

Article References: Immune changes could signal inflammatory bowel disease up to 10 years before diagnosis. Original publication (Bibliographic details unavailable.)

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Keywords: inflammatory bowel disease, Crohn's disease, ulcerative colitis, antibodies, serology, machine learning, biomarkers, herpesvirus, autoantigens, UEG Week 2026, early diagnosis, immune system