Generation of cytotoxic T lymphocytes and cytostatic acting cells in T. annulata-immune cattle.

Cattle immunized against Theileria annulata with schizont containing autologous cell lines are immune to challenge with a homologous parasite strain. Two cell types have been detected in the peripheral blood of the immunized animals: cytotoxic T lymphocytes (CTL) and cytostatic acting cells (CAC). Killing the target cells by CTL is infection associated and is MHC class I restricted. Hence, no cytotoxicity was observed against target cells that were treated with the theilericidal drug buparvaquone or autologous Con A-blasts. The growth inhibition of CAC is MHC unrestricted, and not mediated by cytokine interferon gamma (IFN-gamma).