Immune responses of cattle to Theileria parva (East Coast fever): specificity of cytotoxic cells generated in vivo and in vitro.

Examination of the specificity of cytotoxicity generated in vitro and in vivo against infected bovine lymphoblasts revealed that cytotoxic T lymphocytes (CTL) obtained from cattle immune to Theileria parva recognized parasite-induced alterations associated with major histocompatibility complex (MHC) antigens on the membrane of infected autologous cells. By comparison, cytotoxicity generated in vitro in an autologous Theilerial-lymphocyte culture (AuTLC) contained both CTL and activity akin to that of natural-killer (NK) cells. The addition to the AuTLC of 2 inhibitors of glycosylation, tunicamycin (Tun) and 2-desoxy-D-glucose (2-DOG) abolished both the proliferative response and the generation of cytotoxicity. While the addition of Tun or 2-DOG in conventional cell-mediated lympholysis (CML) assays did not modify the effector function of cytotoxic cells, pretreatment of target cells with either compound prevented lysis by CTL, but not by NK cells. Although parasite-induced antigens have not been purified from infected bovine lymphoblasts, the present study indicated that these are likely to be glycoprotein or carbohydrate in character, and that their recognition on autologous cells is a consistent feature of CTL from immune cattle.