The influence of antigen-presenting cell type and interferon-gamma on priming and cytokine secretion of Leishmania major-specific T cells.

A Leishmania major-specific primary in vitro system that mimics the immune response of infected mice was used to determine the role that dendritic cells, B cells, and macrophages play in L. major T cell priming. Their relative priming potential (in order) was dendritic cells, B cells, and macrophages. Initiating primary in vitro responses with cell populations depleted of either B or dendritic cells modestly enhanced interferon (IFN)-gamma production; deleting both cells markedly enhanced IFN-gamma production. Thus, macrophages were the most effective cell for eliciting L. major Th1 cells. The effects of exogenously added IFN-gamma or neutralizing anti-IFN-gamma were also studied. With cells from genetically susceptible BALB/c mice, IFN-gamma inhibited proliferation and interleukin-4 secretion by T cells, whereas with resistant C57BL/6 cells, IFN-gamma enhanced IFN-gamma secretion. These results could not be explained by differences in IFN-gamma receptor expression.