Differences between N'Dama and Boran cattle in the ability of their peripheral blood leucocytes to bind antibody-coated trypanosomes

Investigations were undertaken to evaluate the immune response of trypanotolerant N'Dama (Bos taurus) and susceptible Boran (Bos indicus) cattle to two Trypanosoma congolense variable antigen types (VATs) expressed in both breeds following tsetse-transmitted challenge. The VAT-specific antibodies of both IgM and IgG₁ isotypes produced by both breeds had similar neutralizing titres. The interaction between immune sera, trypanosomes and freshly isolated peripheral blood leucocytes (PBL) from uninfected N'Dama and Boran animals was studied. It was found that both N'Dama and Boran immune sera were able to induce adherence of trypanosomes to the N'Dama PBL, but not to Boran PBL. The adherence-inducing activity was exhibited by both IgM and IgG₁ antibodies, but IgG₁ antibodies were more efficient in this respect. These results suggest that there are qualitative and/or quantitative differences in the immunoglobulin receptor function of PBL between the two breeds of cattle.