Autoantibodies to Colon in Rats and Human Ulcerative Colitis: Cross Reactivity with Escherichia coli O:4 Antigen

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Abstract
Autoantibodies to germ free rat colon were produced in rats by repeated intra-peritoneal injections with newborn rabbit colon in Freund''s complete adjuvant. Antibodies were assayed by means of indirect hemagglutina-tion of sheep erythrocytes sensitized with a heat stable phenol-water extract of germ free rat colon or by fluorescent antibody staining of rat colon sections. The response of rat colon injected rats was less intense. A few of the rats injected with adjuvant alone also developed an anti-colon titer. Hemagglutination inhibition experiments demonstrated that the antibodies were specific for gastrointestinal antigen and represented autoantibodies in a true sense. They were found to be specific for at least 3 different colon determinants: 1 unique for germ free rat colon, 1 common for rat and rabbit colon, and 1 common for both colons and a polysaccharide from Eschericria coli O: 14, grown on synthetic medium. No or only very weak cross reactions appeared with similar antigens extracted from a number of other E. coli strains. Old Tuberculin and extract of Staphylococcus aureus were inactive. The pattern of reactivity of the rat antibodies was similar to that of patients with ulcerative colitis. Stimulation by cross reacting bacterial antigen may be an important contributing factor for autoantibody formation in this disease.