Around three (3) million Americans suffer from Inflammatory Bowel Disease (IBD), a set of chronic conditions that cause stomach pain and diarrhea, among other disagreeable symptoms. Treatments usually include a suite of medications, including biologics, which can increase a patient’s infection risk. To find better IBD treatments, scientists first need to find the disease’s causes, a hunt that has so far been unsuccessful.
Researchers narrowed in on one of the most common IBD types, Ulcerative Colitis (UC). When they biopsied the colon tissue of UC patients, they noticed that macrophages, a crucial type of immune cell in the gut, were nearly missing. Studying the patients’ poop revealed a likely cause: a toxic substance called aerolysin that gets secreted by a specific genus of bacteria and damages the macrophages so that the gut is susceptible to inflammation. Lab experiments infecting mice with the bacteria caused worsening UC symptoms, while administering antibodies targeting aerolysin alleviated them.
The final confirmation of aerolysin’s destructive role came from fecal samples and colon biopsies of hundreds of UC patients and healthy individuals; more than 70% of patients had aerolysin-producing bacteria, while only 12% of healthy people did.
“Directly targeting these microbes and their toxins could be a promising avenue for treating IBD without inhibiting patients’ immune systems with biologics, such as antibodies, and steroid drugs,” wrote immunologists Sonia Modilevsky and Shai Bel in a related Science Perspective.
REFERENCE: Science Advisor; 20 NOV 2025; Sonia Modilevsky and Shai Bel