Submitted to: International Conference on Mycobacterium bovis
Publication Type: Abstract Only
Publication Acceptance Date: 8/14/2000
Publication Date: N/A
Technical Abstract: Despite highly successful eradication efforts in several countries, Mycobacterium bovis infection of cattle remains a significant health concern worldwide. Immune mechanisms of resistance to and/or clearance of M. bovis infection of cattle, however, are unclear. Recent studies have provided evidence supporting a role for CD4+, CD8+, and gamma/delta TCR+ T cells in the response of cattle to M. bovis. In the present study, we utilized a flow cytometric-based proliferation assay to determine the relative contribution of individual lymphocyte subsets in the response to M. bovis infection and/or sensitization with mycobacterial purified protein derivative (PPD). Peripheral blood mononuclear cells (PBMC) from M. bovis-infected cattle proliferated in response to in vitro stimulation with PPD. CD4+ T cells and gamma/delta TCR+ cells were the predominate subsets of lymphocytes responding. Gamma/delta TCR+ cells also proliferated in non-stimulated cultures; however, the gamma/delta TCR+ cell proliferative response of infected cattle was significantly (P less than 0.05) greater in PPD-stimulated cultures as compared to non- stimulated cultures. Intradermal injection of PPD for comparative cervical testing (CCT) induced a boost in the CD4+ cell, but not gamma/delta TCR+ cell, proliferative response of infected cattle. Injection of PPD for CCT did not, however, elicit a proliferative response in non-infected cattle. These data indicate that CD4+ and gamma/delta TCR+ cells of M. bovis-infected cattle proliferate in a recall response to PPD and that the CD4+ cell response is boosted by intradermal injection with PPD for CCT.