Ulcerative colitis: specific antibodies against a colonic epithelial Mr 40,000 protein

A colon tissue-bound disease specific IgG (CCA-IgG) antibody can be eluted from the colonic tissue of patients with ulcerative colitis (UC). CCA-IgG recognizes an Mr 40,000 protein present in both normal and diseased colon. Using an anti-Mr 40,000 murine monoclonal antibody this protein has been localized exclusively in colonic epithelial cells mainly along the baso-lateral domains of plasma membrane. Non-colonic epithelial tissues from 12 different organs including small intestine did not react with the anti-Mr 40,000 monoclonal antibody. The Mr 40,000 protein is present in the RPMI-4788 colon cancer cells but not in HeLa. The antibody dependent cell-mediated cytolysis by UC sera against RPMI-4788 cells was inhibited by anti-Mr 40,000 polyclonal antibody. These findings suggest that CCA-IgG and the Mr 40,000 colonic epithelial protein are involved in an autoimmune reaction and may be important in the pathogenesis of UC.