Colitis development in IL-2/IFN-γ–KO mice. Hematoxylin and eosin stains of the descending colon from 27-day-old IL-2–KO (A) and IFN-γ–KO (B) mice, and a 72-day-old IL-2/IFN-γ–KO (C) mouse with a prolapsed rectum. Arrow indicates area of ulceration and underlying inflammation. (D) Cytokine RNAs were examined in the descending colon by real-time PCR. Data were normalized to HPRT and WT was set to 1.