Activation of bovine peripheral blood macrophages in Theileria sergenti-infected calves.

Macrophage activation in Theileria sergenti-infected calves was studied by testing the production of oxygen metabolites in macrophages following specific and non-specific stimulation with T sergenti merozoites or zymosan, respectively. Six calves were inoculated with merozoites and three calves with sporozoites. All showed significant macrophage activation within one month after inoculation (P less than 0.05). Activation of macrophages appeared earlier than parasitaemia or the peak of antibody titre against T sergenti. The highest chemiluminescence response, indicative of macrophage activation, was observed when the merozoites were opsonised with immune sera.