MHC class II-restricted, CD4(+) T-cell proliferative responses of peripheral blood mononuclear cells from Mycobacterium bovis-infected white-tailed deer

White-tailed deer are significant wildlife reservoirs of Mycobacterium bovi s for cattle, predators, and, potentially, humans. Infection of cattle with M, bovis stimulates an antigen-specific T-cell response, with both CD4(+) and CD8(+) cells implicated in protective immunity. Few studies, however, h ave examined lymphocyte subset responses to experimental M. bovis infection of white-tailed deer. In this study, a flow cytometric proliferation assay was used to determine the relative contribution of individual peripheral b lood mononuclear cell subsets of M. bovis-infected white-tailed deer in the recall response to M. bovis antigen. Naive deer were challenged with M. bo vis by cohabitation with infected deer. These M. bovis-challenged deer deve loped significant in vivo (delayed-type hypersensitivity) and in vitro (pro liferative) responses to M, bovis purified protein derivative (PPD). At nec ropsy, typical tuberculous lesions containing M. bovis were detected within lungs and lung-associated lymph nodes of infected deer. The predominant su bset of lymphocytes that proliferated in response to in vitro stimulation w ith PPD was the CD4(+) subset. Minimal proliferative responses were detecte d from CD8(+), gamma delta6 TCR+, and B-cells. Addition of monoclonal antib odies specific for MHC II antigens, but not MHC I or CD1 antigens, abrogate d the proliferative response. Together, these findings indicate that while CD4(+) cells from infected deer proliferate in the recall response to M. bo vis antigens, this response is not sufficient to clear Arl. bovis and immun ologic intervention may require stimulation of alternate subsets of lymphoc ytes. (C) 2000 Elsevier Science B.V. All rights reserved.