Antibody patterns could predict inflammatory bowel disease a decade early

Researchers have found a way to see inflammatory bowel disease coming years before it arrives. In a study presented at UEG Week 2026 in Barcelona, scientists identified distinct patterns in a person's antibodies up to a decade before they receive a diagnosis of either Crohn's disease or ulcerative colitis—the two main forms of IBD. The discovery suggests that the immune system begins its slow drift toward these chronic conditions long before the first symptoms appear, and that tracking these changes might one day allow doctors to intervene far earlier than they can today.

IBD is a group of chronic inflammatory conditions affecting the digestive system, driven by abnormal immune responses that cause ongoing damage to the gut. While researchers have long suspected that IBD develops gradually over time, the precise immune changes that occur during this hidden phase have remained largely unmapped. To chart this territory, a team led by Dr. Arno Bourgonje at the Icahn School of Medicine at Mount Sinai analyzed 2,000 blood serum samples collected from 500 people—200 who later developed Crohn's disease, 200 who developed ulcerative colitis, and 100 healthy controls matched for age and sex. The samples were taken at the moment of diagnosis and also at roughly two, four, and ten years before diagnosis.

The researchers screened these samples against approximately 357,000 different antigens—molecular markers derived from microbes, viruses, food, and immune-related sources. Across all 2,000 samples, they identified 123,980 unique antibodies. What emerged was striking: people who would later develop IBD showed significantly lower antibody diversity compared to healthy controls, and this difference was visible a full decade before their disease was diagnosed. The antibody signatures were distinct enough that researchers could tell Crohn's disease from ulcerative colitis based on the patterns alone.

In Crohn's disease, the researchers observed elevated antibody responses against herpesviruses and flagellin—a protein found in bacterial flagella—particularly in people who would go on to develop complicated forms of the disease or disease localized to the ileum. At the same time, antibody responses to encapsulated bacteria steadily declined as diagnosis approached. In ulcerative colitis, the pattern differed: antibody responses against herpesviruses and autoantigens rose over time, while reactivity to encapsulated pathogens fell. These signatures were not random noise. When researchers fed them into machine-learning models, the models could distinguish people destined to develop Crohn's disease from healthy controls with 90 percent accuracy, and those destined for ulcerative colitis with 84 percent accuracy—all based on blood samples taken up to ten years in advance. The models could even predict which Crohn's patients would develop complicated disease, achieving 85 percent accuracy.

The implications are substantial. If these antibody patterns truly reflect the early immune changes that precede IBD, they could become the basis for screening people at high risk, identifying which patients might benefit from aggressive early treatment, and potentially even preventing the disease from developing at all. Bourgonje noted that the finding that complicated Crohn's disease is associated with a distinct antibody signature years before symptoms appear suggests the disease's severity is not simply a consequence of how long inflammation has been present, but rather reflects something fundamental about the immune trajectory from the beginning.

Yet the researchers are careful about what they claim. They emphasize that this is proof of principle, not yet a clinical tool. Before any antibody test could be offered to patients, the signatures must be validated in larger, more diverse populations followed over time. The antibody patterns must be tested alongside genetic markers and other blood-based biomarkers to see whether they add real predictive value. The test itself must be translated into a form that is reproducible and affordable. And most critically, researchers must demonstrate that actually using such a test to identify at-risk people and treat them earlier leads to better outcomes. That final step—showing that early detection actually changes the course of disease—remains the essential hurdle. For now, the antibody signatures represent a window into the immune system's long prelude to IBD, and a direction for research to follow.