Since in the gut of IBD patients, high Smad7 abrogates TGF-β1 activity [40] and mucosal inflammation is marked by high IL-12 and IL-23 [3,41], it is conceivable that IFN-γ-producing cells seen in IBD tissue originate in part from pre-existing IL-17A-expressing T cells. The gene discussed is TGFB1; the disease is inflammatory bowel disease.