CD4 and colitis: Consistent with our prior observations pointing to the requirement of intact IL-21/IL-21R signaling in the regulation of colitis following C. rodentium infection,6 the expression of IFN-γ and IL-12Rβ2, but not IL-12Rβ1, was impaired in distal cLP CD4+ T cells of Il21r−/− mice following C. rodentium infection.