EVIDENCE FOR STRAIN SPECIFICITY IN CYTOTOXIC T-LYMPHOCYTE-MEDIATED, MAJOR HISTOCOMPATIBILITY COMPLEX CLASS I-DEPENDENT KILLING OF THEILERIA-ANNULATA-INFECTED CELLS

Cattle immunised against Theileria annulata with one parasite strain h ave been found to be immune to re-challenge with different strains of the parasite. However, recent evidence of apparent strain specificity has been documented in cattle immunised with attenuated parasite-infec ted cells. In this study the strain specificity of major histocompatib ility complex class I-restricted cytotoxic T-lymphocytes (CTL), a majo r anti-parasite effector mechanism, was examined. CTL generated follow ing challenge with the Hissar (Indian) strain effectively lysed autolo gous cells infected with this strain of the parasite. However, CTL wer e less effective against cells infected with the Gharb (Moroccan) stra in and showed virtually no reactivity against the Ankara (Turkish) str ain, providing the first direct evidence for strain specificity in imm une responses against T. annulata.