Decreased expression of protectin (CD59) in gut epithelium in ulcerative colitis and Crohn's disease

Without adequate protection, the cells of the human body would be susceptib le to destruction by the complement system. The main defense against comple ment lysis is a molecule called protectin (CD59) that is widely distributed in human tissues. Because the complement system has been suggested to be i nvolved in the pathogenesis of inflammatory bowel diseases, we examined the expression of protectin in the colonic epithelium of patients with ulcerat ive colitis or Crohn's disease and controls, Colorectal specimens from 6 pa tients with ulcerative colitis, 8 patients with Crohn's disease, and 4 cont rols were obtained from surgical resections. Frozen sections of the specime ns were immunostained for protectin using the Bric 229 monoclonal antibody. The expression of protectin was found to be decreased in the epithelium of patients with ulcerative colitis. In patients with Crohn's disease, the ep ithelial expression of protectin was decreased in diseased areas of gut whi le the expression did not significantly differ from that in controls in mac roscopically normal areas. There was no difference in the expression of pro tectin on vascular endothelium, mononuclear cells, or smooth muscle. The re duction in epithelial expression of protectin in patients with ulcerative c olitis or Crohn's disease may render epithelial cells vulnerable to complem ent lysis and lead to the destruction of gut epithelium as seen typically i n these diseases. Copyright 1999 by W.B. Saunders Company.