Aggravation of intestinal inflammation by depletion/deficiency of T cells in different types of IBD animal models

The role of T cells in inflammatory bowel disease (IBD) is still controversial. Although T cells induce IBD in immunodeficient animals, others suggest a protective role of T cells. Therefore, this study was conducted in order to elucidate the effect of T cell depletion/deficiency on different IBD animal models. Mice depleted of or deficient in T cells were exposed to dextran sodium sulfate (DSS) in order to induce colitis. In addition, T cells were depleted in mice with terminal ileitis (TNF ) or colitis due to interleukin 2 deficiency (IL-2 ko). Finally, DSSinduced colitis was studied in mice deficient in interferon gamma (IFNko) upon T cell depletion. Depletion of T cells aggravated DSS-induced colitis and terminal ileitis of TNF ARE mice. Exacerbated DSS-induced colitis was also found in T cell-deficient mice. IL-2 ko mice showed increased mortality upon early (starting at 4 wk of age) but not late depletion (starting at 8 wk of age). Early T cell depletion or deficiency resulted in increased IFNproduction by both lamina propria lymphocytes and splenocytes in every model investigated herein. In IFNko mice, T cell depletion did not affect the development and course of DSS-induced colitis. The protective effect of T cells in IBD was confirmed in various IBD animal models. Particularly, during the early phase of intestinal inflammation, T cells appear to be important. The mechanism seems to involve the control of IFNproduction and epithelial regeneration. J. Leukoc. Biol. 81: 000–000; 2007.