Human colonic intra-epithelial lymphocytes are suppressor cells.

Human colonic intra-epithelial lymphocytes (IEL) suppress the proliferation of autologous lamina propria lymphocytes, but not autologous peripheral blood mononuclear cells, when stimulated with phytohaemagglutinin. This suppressor function is mediated by a CD8-dependent soluble factor and is not related to the expression of the gamma delta T cell receptor. These findings may be relevant to the induction of mucosal tolerance. However, there is no defect in suppressor activity of colonic IEL in inflammatory bowel disease