Cellular immune responses of cattle to Cowdria ruminantium.

Peripheral blood mononuclear cells (PBM) from cattle immunised against Cowdria ruminantium infection (Heartwater), proliferated in vitro in the presence of either infected autologous endothelial cells pre-treated with T cell growth factors to induce MHC class II expression, or infected autologous monocytes. Proliferation was not observed in PBM cultured with a soluble extract of the agent, but PBM responded to two recombinant antigens of C. ruminantium, namely a 32 kDa (MAP1) and a 21 kDa antigen (MAP2). We hypothesize that infected endothelial cells and monocytes present Cowdria antigens to specific lymphocytes during infection and thereby play a role in the pathogenesis/immune response to the pathogen.