Cytotoxicity of mononuclear cells for autologous colonic epithelial cells in colonic diseases

Macrophage-depleted isolates of mononuclear cells from the colonic mucosas of 25 patients with chronic ulcerative colitis or Crohn's colitis were cytotoxic for autologous colonic epithelial cells, as were mononuclear cells from their peripheral blood. This was markedly reduced by trypsinizing the mononuclear cells and was restored by a 1-h exposure of the trypsinized cells to 25% vol/vol heat-inactivated autologous plasma. Trypsinization of the target cells had no effect on cytotoxicity. Mononuclear cells that adhered to plates coated with heat-aggregated immunoglobulin G contained the effectors. It was suggested that this phenomenon was a form of antibody-dependent cell-mediated cytotoxicity in which the effector cells rather than the targets were “armed” by antibody. Cytotoxicity for autologous colonic epithelial cells was also shown by colonic mononuclear cells but not by mononuclear cells from the peripheral blood in a group of 40 patients with colorectal tumors, and by 1 of 4 patients with diverticulitis. This cytotoxicity was markedly reduced by trypsinizing the colonic mononuclear cells but was not restored by exposing the trypsinized cells to autologous plasma. Colonic mononuclear cells that adhered to plates coated with heat-aggregated immunoglobulin G contained the effectors. It seems likely that this cytotoxicity was spontaneous cell-mediated cytotoxicity.