Dendritic cells induce CD4(+) and CD8(+) T-cell responses to Mycobacteriumbovis and M-Avium antigens in Bacille Calmette Guerin vaccinated and nonvaccinated cattle

Few data are available regarding the induction of memory T-lymphocyte respo nses in cattle following Bacille Calmette Guerin (BCG) vaccination. Studies of the immune response induced by BCG vaccination provide an insight into the basis of antimycobacterial immunity that could be exploited for the dev elopment of more effective vaccination strategies. We used autologous dendr itic cells (DC) infected with Mycobacterium bovis Bacille Calmette Guerin ( BCG) or pulsed with purified protein derivative from M. bovis (PPD-B) or M. avium (PPD-A) to assess responses of CD4(+), CD8(+) and WC1(+) gamma delta TCR+ lymphocytes from BCG vaccinated and nonvaccinated cattle. Mycobacteri a-specific CD4(+) and CD8(+), but not WC1(+) gamma delta TCR+, memory T lym phocytes were demonstrated in BCG-vaccinated cattle. CD4(+) and CD8(+) lymp hocytes proliferated and produced interferon (IFN)-gamma in response to BCG -infected or PPD-B-pulsed DC. Proliferative responses were greater for CD4( +) than CD8(+) lymphocytes, although secretion of IFN-gamma was higher from the CD8(+) T cells. Responses to PPD-A-pulsed DC were lower, with no CD8() response. Lymphocytes from nonvaccinated calves were also stimulated to p roliferate by BCG-infected DC, although the magnitude of proliferation was lower. The findings suggest that immunity to M. bovis induced by BCG vaccin ation in cattle may involve CD8(+) memory T cells which produce IFN-gamma, as well as CD4(+) memory T cells.