Tropical theileriosis: cytotoxic T lymphocyte response to vaccination.

Cattle which survive an infection with Theileria annulata become effectively immune to challenge with the same parasite strain, and are thought to be protected against a heterologous strain of the parasite. T-cells play a crucial role in both induction and maintenance of immunity to T. annulata. The generation of cytotoxic T lymphocytes (CTL) is closely related to the control of the infection - macroschizont-infected cells are killed in an MHC class I restricted manner. Any strain-specificity induced by immunisation is likely to be manifested by CTL. Besides CTLs, CD4+ T-cells also play an important role in protective immunity to T. annulata infection.