In an elegant study, Neurath’s group showed that CD69+CD103+ TRM cells accumulated in the mucosa of patients with IBD and produced high levels of inflammatory cytokines (i.e., IFN-γ, IL-13, IL-17A, and TNF-α), and the presence of CD4+CD69+CD103+ TRM cells was predictive of IBD exacerbations. This evidence concerns the gene CD4 and inflammatory bowel disease.