T-CELL-MEDIATED IMMUNITY AND TISSUE-DAMAGE IN THE GUT

The mucosal immune system is well equipped to mediate cell-mediated hy persensitivity reactions since T cells and antigen presenting cells ar e abundant in Peyer's patches and mucosa. Activation of T cells with l ectins in explants of human fetal small intestine grown in vitro rapid ly induces tissue damage and thus may be a model for the cell-mediated immune reaction which is ongoing in the lamina propria in active Croh n's disease. This is evidenced by the high frequency of interleukin-2 and interferon gamma-secreting cells which are abundant in Crohn's dis ease but not ulcerative colitis.