Submitted to: Research Workers in Animal Diseases Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 11/8/1998
Publication Date: N/A
Technical Abstract: Mycobacterium avium subsp. paratuberculosis infection of cattle results in a chronic granulomatous enteritis. Clinical disease (i.e., cachexia, diarrhea, and high fecal bacterial counts) is preceded by a lengthy subclinical stage of disease. Immunologic mechanisms associated with progression of infected cattle from subclinical to clinical disease are unclear. In this study, a cellular proliferation assay in combination wit flow cytometry was used to compare peripheral blood lymphocyte responses of cattle with subclinical paratuberculosis to responses of cattle with clinical paratuberculosis. B cells from cattle with subclinical disease proliferated vigorously upon stimulation with M. avium subsp. paratuberculosis antigen with up to 12.4% of the total B cells responding. However, B cells from cattle with clinical disease did not proliferate upon antigen stimulation despite good proliferation to Con-A stimulation. In addition, animals with clinical disease had higher percentages of peripheral blood B cells than either control or subclinically-affected animals. B cells from non-infected animals did not proliferate upon M. avium subsp. paratuberculosis antigen stimulation. Thus, it appears that B cell proliferative responses can be used as a sensitive indicator of subclinical Johne's disease. Furthermore, immunologic mechanisms responsible for the antigen-specific unresponsiveness of peripheral blood B cells may be significant in the eventual progression from subclinical to clinical Johne's disease in cattle.