Scientists solve a 30-year mystery behind inflammatory bowel disease

The findings indicate that IBD is not simply one disease. Instead, it appears to include several biologically distinct conditions that develop through different processes in the body. Identifying these differences could make it possible to provide treatments tailored to the specific cause of each patient’s illness.

In a study published in the New England Journal of Medicine, researchers examined more than 4,900 people with IBD and identified two important findings. First, some patients produce antibodies that interfere with interleukin-10 (IL-10), an essential protein that helps prevent excessive inflammation. Second, this autoimmune reaction explains how one of the strongest known genetic risk factors for IBD contributes to the disease.

Under normal circumstances, IL-10 acts as a chemical messenger between cells, helping the immune system regulate inflammation. However, certain antibodies can block its activity, effectively disabling one of the body’s built-in safeguards against excessive immune responses. Without this protection, inflammation can persist and become difficult to control.

Hidden Antibodies Reveal a Cause of Inflammatory Bowel Disease

Inflammatory bowel disease includes Crohn’s disease and ulcerative colitis, two chronic conditions that affect approximately 500,000 people in the UK and millions more around the world.

Symptoms often first appear during adolescence or early adulthood, and patients may face lifelong medical challenges. Managing the disease can involve repeated hospital visits, medications that suppress immune activity, and sometimes surgery. Although treatments have improved, many people must try several different therapies without achieving lasting relief. This places a substantial burden on patients and creates significant costs for healthcare systems.

The researchers discovered that approximately 3.5% of patients with IBD had elevated levels of antibodies that neutralize IL-10. These antibodies were detected in people with both Crohn’s disease and ulcerative colitis, but not in healthy individuals.

Based on the prevalence of IBD in the UK, the researchers estimate that 15,000 to 20,000 patients nationwide could carry these harmful antibodies.

Scientists Solve a 30-Year Genetic Mystery

The investigation also revealed a strong association between the IL-10-blocking antibodies and a genetic variant called HLA-DRB1*01:03.

Scientists at Oxford first connected this genetic variant to a severe form of inflammatory bowel disease 30 years ago. However, the biological process linking the gene to the condition had remained unclear.

The new results help resolve that longstanding mystery. People who carry HLA-DRB1*01:03 are substantially more likely to develop antibodies that interfere with IL-10, providing an explanation for how this genetic risk factor can contribute to severe intestinal inflammation.

Professor Holm Uhlig, a pediatric gastroenterologist and Director of the Centre for Human Genetics at the University of Oxford’s Nuffield Department of Medicine, was a senior author of the study.

“We’ve suspected an important role of interleukin 10 in patients with inflammatory bowel disease for decades. The study now provides clear evidence and contributes the missing link between a well-known genetic variant that had been linked to severe inflammatory bowel disease in the past and the very recently discovered autoimmunity to interleukin 10.”

“Understanding what drives the inflammation, provides a clear explanation for disease in this group of people and opens the door to new treatments that target the autoantibodies themselves or cells that produce those autoantibodies.”

How Earlier Discoveries Helped Explain Severe IBD

The findings build on more than a decade of research into rare inherited disorders that disrupt the body’s ability to control inflammation.

Sophie Hambleton, Professor of Pediatrics and Immunology at Newcastle University, explained that studying these uncommon conditions provided important clues about the mechanisms involved in more widespread forms of IBD.

“This discovery shows how the study of rare, inherited disorders can shed new light on common conditions. The groundwork was laid over 10 years ago when genetic defects in IL-10 or its receptor were found in young children with severe IBD. Later, we realized that neutralizing autoantibodies against IL-10 were mimicking this effect in 2 little girls with colitis.”

These earlier observations helped researchers recognize that antibodies blocking IL-10 could produce effects similar to inherited defects involving the same protein or its receptor. The latest study now establishes the importance of this mechanism in a larger group of patients with inflammatory bowel disease.

A Blood Test Could Lead to More Targeted IBD Treatments

Beyond explaining a previously mysterious cause of intestinal inflammation, the discovery could have important implications for patient care.

Researchers believe the results provide a foundation for developing a blood test that identifies people whose disease is associated with antibodies against IL-10. Such a test could help doctors recognize these patients earlier and select treatments that address the underlying immune malfunction.

Dr. Rainer Doffinger, a clinical immunologist at Cambridge University Hospitals NHS Foundation Trust, highlighted the potential benefits for both patients and healthcare systems.

“By identifying patients early and giving them targeted treatment, we could reduce reliance on expensive ongoing therapy and prevent complications. Even modest reductions in biologic treatment, admissions and surgery could translate into savings of many millions of pounds annually for the NHS, alongside the major benefits for patients through fewer interventions, improved quality of life or even durable remission.”

Targeting the antibodies themselves, or the immune cells responsible for producing them, could offer a new treatment strategy for this particular group of patients. The approach could potentially reduce the need for repeated therapies, hospital admissions, and surgery while improving the chances of sustained disease control.

Professor Simon Travis, Professor of Clinical Gastroenterology at the University of Oxford and the Kennedy Institute of Rheumatology, emphasized the significance of identifying a specific biological cause of IBD.

“This is the most exciting discovery in a lifetime specialising in IBD. It means that we can now identify a group where we know what is causing the disease and that creates a real opportunity to change how we manage this disease.”

The research marks an important advance toward personalized treatment for inflammatory bowel disease. Rather than relying primarily on symptoms to guide medical decisions, doctors may eventually be able to use biological testing to determine what is driving inflammation in individual patients and choose more appropriate therapies.

The study involved researchers from the Nuffield Department of Medicine at the University of Oxford, Newcastle University’s Translational and Clinical Research Institute, and the Department of Immunology at Cambridge University Hospitals NHS Foundation Trust.

Funding was provided through the National Institute for Health and Care Research (NIHR) Biomedical Research Centres in Oxford, Cambridge, and Newcastle.