Inflammatory bowel disease [IBD] is thought to be perpetuated by intestinal microbial dysbiosis leading to episodic colitis [ulcerative colitis, UC] or localised inflammation anywhere along the gastrointestinal [GI] tract [Crohn’s disease, CD], mediated by Th17 or other subsets of CD4 T cells.3,4 Disease aetiology involves interaction of multiple genetic susceptibilities with environmental factors, including diet and lifestyle factors, that can affect the microbiota. Here, CD4 is linked to inflammatory bowel disease.