Influence ofMycobacterium aviumsubsp.paratuberculosison Colitis Development and Specific Immune Responses during Disease

The granulomatous and intramural inflammation observed in cases of inflammatory bowel diseases (IBD) and veterinary Johne's disease suggests thatMycobacterium aviumsubsp.paratuberculosisis a causative agent. However, an incomplete understanding of the immunological steps responsible for the pathologies of IBD makes this conclusion uncertain. Sera from interleukin-10-deficient (IL-10−/−) mice with spontaneous colitis displayed significantly higherM. aviumsubsp.paratuberculosis-specific immunoglobulin G2a antibody responses than did sera from similar mice without disease. Pathogen-free IL-10−/−mice received control vehicle or the vehicle containing heat-killed or liveM. aviumsubsp.paratuberculosis. Mucosal CD4+T cells from the mice that developed colitis proliferated and secreted higher levels of gamma interferon and tumor necrosis factor alpha after ex vivo stimulation with a Vβ11+T-cell receptor-restricted peptide from the MPT59 antigen (Ag85B) than those secreted from cells from mice before the onset of colitis. The data from this study provide important information regarding the mechanisms of colitis in IL-10−/−mice, which are driven in part by Ag85B-specific T cells. The data suggest a plausible mechanism of Ag-specific T-cell responses in colitis driven by potent Ags conserved inMycobacteriumspecies.