CD4 and colitis: In addition to the increased corticosterone levels, CD4+ T cells from antibiotic-treated mice showed altered expression of stress response-, cellular metabolism-, cell-cycle regulation-, and cell death-related genes and induced an earlier onset of colitis, when transferred to recombinase activator gene 1-deficient mice, which develop colitis in response to CD4+ T cells owing to their defects in the immunoregulation of mucosal T-cell responses [128].