ANTIBODIES AGAINST MYCOBACTERIUM-PARATUBERCULOSIS IN CROHNS-DISEASE

Until recently the investigation of serological responses to mycobacte ria in patients with Crohn's disease has been hindered by the consider able degree of cross-reactivity between antigens of M. paratuberculosi s, and other mycobacterial subspecies. We evaluated the serological re sponse of Crohn's disease patients to a recently identified species-sp ecific 18 kDa protease-resistant antigen corresponding to M. paratuber culosis bacterioferritin. The 18 kDa antigen was purified from M. para tuberculosis as previously described. Serum was obtained from 40 patie nts with Crohn's disease, 15 with ulcerative colitis, 25 coeliac patie nts, and 21 normal blood donors. Antibody levels were measured by enzy me-linked immunosorbent assay (ELISA), with anti-human IgA and IgG alk aline phosphatase conjugate. Antibody titres were expressed as the dil ution giving 1/3 of the plateau binding value of a standard positive s erum (MT/3). Disease activity of the Crohn's disease cases was assesse d using the Harvey-Bradshaw index. There was no statistically signific ant elevation of the mean IgG or IgA MT/3 titres of Crohn's disease pa tients over controls. No patients had antibody titres greater than two standard deviations above the mean control MT/3 titres, and there was no significant correlation between Crohn's disease activity and level of antibody titres. These findings make it unlikely that M. paratuber culosis is of primary pathogenic importance in Crohn's disease.