Effect of intestinal resection on serum antibodies to the mycobacterial 45/48 kilodalton doublet antigen in Crohn's disease.

Interest in the role of mycobacterial infection in Crohn's disease has been revived by the cultural detection of Mycobacterium paratuberculosis in patients with Crohn's disease. This hypothesis was examined serologically using assays with high specificity for Crohn's disease. The effect of intestinal resection on serum antibodies specific for Crohn's disease was investigated with an immunoblot assay and an enzyme linked immunosorbent assay using the 45/48 kilodalton doublet antigen of Mycobacterium tuberculosis. Antibodies were detected in 64.7% of patients with Crohn's disease (n = 17), 10% of patients with ulcerative colitis (n = 10), 5% of patients with carcinoma of the colon (n = 20), and none of 10 healthy subjects with the immunoblot assay. Statistical comparison of the Crohn's disease patients with each control group resulted in p = 0.0000236. Immunoglobulin G was essentially unchanged 75 days (mean) after surgery. After more than 180 days, however, the antibody response was reduced in all of five patients studied, and was no longer demonstrable in two of them (40%). Simultaneously, the Crohn's disease activity index (CDAI) decreased. Both the high specificity of this assay for Crohn's disease and the diminished antibody response after intestinal resection in parallel with decreased CDAI support a mycobacterial aetiology of Crohn's disease.