Differential expression of surface membrane antigens on bovine monocytes activated with recombinant cytokines and during Trypanosoma congolense infection

The expression of surface membrane antigens on peripheral blood monocytes ( PBM) of cattle of the Boran and N'Dama breeds activated with recombinant cy tokines (TNF-alpha and IFN-gamma) and during experimental infection with Tr ypanosoma congolense was investigated using monoclonal antibodies (MoAbs) a nd fluorescein-activated cell sorter (FACS). The surface antigens investiga ted were C3bi receptor, major histocompartibility (MHC) II complex (la anti gen) and two monocyte/macrophage (M phi) differentiation antigens. The study revealed that both cytokines caused the enhancement of the expres sion of all the PBM surface antigens studied. rBolFN-gamma at low concentra tions was more efficient in causing the activation of PBM. While the PBM of Boran cattle were more significantly activated to express the C3bi recepto r vis-a-vis the la antigen than N'Dama cattle, the reverse was the case wit h the PBM of N'Dama cattle which expressed more la antigens than Boran PBM. Similar results were observed during T:congolense infection in the two bre eds of cattle. The significantly higher expression of C3bi receptor and correspondingly lo wer la antigen expression by the PBM of Boran cattle, both during trypanoso mosis and in vitro may be responsible for the higher rate of erythrocyte ph agocytosis, hence the development of more severe anaemia by Boran cattle du ring trypanosomosis than N'Dama. In addition, the expression of significant ly higher numbers of la antigen by N'Dama M phi, hence are more able to pro cess, present and initiate better trypanosome antigen-specific immune respo nse than Boran cattle during infection. These two attributes are known gene tic characteristics of trypanotolerance in cattle.