Peripheral cell‐mediated immune response to mycobacterial antigens in inflammatory bowel disease

SUMMARY A mycobacterial etiology has been proposed In Crohn's disease (CD). We have sought evidence of increased or modified T lymphocyte immune responses to Mycobacterium tuberculosis and Myco. paratuber culosis in patients with CD (n = 13), compared with ulcerative colitis (UC; n = 17) and controls (n = 17). Peripheral blood cells were cultured with phytohaemagglutinin (positive mitogen control), mycobacterial purified protein derivative (PPD) preparations, lysates., column fractions and whole, heat‐killed bacteria. Responses of T cells and T cell subsets were assessed by expression of activation markers (CD25. CD69). coupled with blastogenesis assays (3H‐thymidine uptake) and estimates of proliferation. Virtually all patients responded to Myco. paratuberculosis and Myco. tuberculosis antigens. There were no significant differences between patient groups, although there was a very high overall correlation (r = 0.95; P