Abstract

In patients with ulcerative colitis a colon tissue bound IgG and serum antibodies against an Mr 40,000 colonic protein(s) has been identified. Using an anti-Mr 40,000 protein monoclonal antibody, 7E12H12, by an immunocytochemical method, the protein was localised in human tissue exclusively to colonic epithelial cells. In this study the presence of the Mr 40,000 protein was assessed in experimental animals by the direct and inhibition enzyme linked immunosorbent assays (ELISAs) using the anti-Mr 40,000 protein monoclonal antibody, 7E12H12 (IgM isotype). In addition, a total of 129 specimens including colon, small intestine, gall bladder, biliary tract, and kidney from nine strains of rats and mice, and from human tissue were studied by the immunocytochemical method using 7E12H12. All colon specimens from both humans and animals reacted with 7E12H12 in the immunocytochemical and ELISA assays. None of the non-colonic organs reacted with 7E12H12. While in human colon 7E12H12 recognised the absorptive epithelial cells, in all the animals it recognised mainly the colonic goblet cells. Extracts of animal colon but not of small intestine inhibited the binding of 7E12H12 to the human colon extract. This study shows the presence of an organ specific Mr 40,000 colonic epithelial protein(s) in humans and experimental animals. A differing cellular localisation of the Mr 40,000 protein(s) in human v animal tissue was also shown. Further characterisation of the Mr 40,000 protein(s) may provide important clues regarding the autoimmune mechanisms in ulcerative colitis.