Studies on the induction and specificity of cytotoxicity to Theileria -transformed cell lines.

Abstract

Several autologous and allogeneic Theileria-transformed cell lines were tested for their ability in vitro to induce DNA synthesis and cytotoxic cells in bovine peripheral blood lymphocyte populations. Both autologous and allogeneic cell lines strongly induced DNA synthesis in responding cells from normal and Theileria-immune cattle. Some Theileria-transformed cells were better stimulators than others in both autologous and allogeneic situations. The responding lymphocytes were non-B lymphocytes and were T or null lymphocytes as determined by combined autoradiography/immunofluorescence. Antisera or monoclonal antibodies specific for Theileria macroschizont antigens did not influence the lymphocyte stimulation.Both autologous and allogeneic Theileria-transformed cell lines also induced cytotoxic cells in vitro but only when responder cell populations were from Theileria-immune animals. The generation of cytotoxicity in vitro could thus be used as a test for bovine immunity to Theileria parva. Cytotoxicity was always strongest when the target cells were syngeneic with the effector population, even when allogeneic stimulators were used. Specificity analysis of cytotoxic cells generated in autologous responder/stimulator combinations showed that both genetically restricted and nonrestricted components were present and that these were likely due to distinct effector populations. In addition, the genetically restricted cytotoxicity was parasite-specific. The implications of these findings for development of vaccines for East Coast fever are discussed.