CD8+ T-cell profiling predicts prognosis in patients with Crohn's disease and ulcerative colitis (5, 57) and we observed the main contribution to colitis development was mediated by cytokine producing, proliferative, CD8+ Gab2/3−/− T-cells in the intraepithelial compartment. The gene discussed is GAB2; the disease is ulcerative colitis.