A life-cycle stage-specific antigen of Theileria parva recognized by anti-macroschizont monoclonal antibodies.

Four monoclonal antibodies, raised against macroschizonts of Theileria parva, were studied to characterize their antigen binding specificity. The indirect fluorescent antibody test showed that the antigen(s) recognized were present in the macroschizont stage of the parasite life-cycle but not in piroplasm, kinete or sporozoite stages. Immunoblot analysis of macroschizont stage antigens suggested that all four antibodies recognized the same antigen. This was a molecule which varied in molecular mass between different parasite stocks, ranging from 68,000 to 95,000 Da. The antigen was localized by immunoelectron microscopy to the surface of the intracellular macroschizonts.