Abstract:
The expression of surface membrane antigens on peripheral blood monocytes (PBM) of cattle of the
Boran and N'Dama breeds activated with recombinant cytokines (TNF-α and IFN-γ) and during experimental
infection with Trypanosoma congolense was investigated using monoclonal antibodies
(MoAbs) and fluorescein-activated cell sorter (FACS). The surface antigens investigated were C3bi
receptor, major histocompartibility (MHC) II complex (Ia antigen) and two monocyte/macrophage (MΦ)
differentiation antigens.
The study revealed that both cytokines caused the enhancement of the expression of all the PBM
surface antigens studied. rBoIFN-γ at low concentrations was more efficient in causing the activation
of PBM. While the PBM of Boran cattle were more significantly activated to express the C3bi receptor
vis-a-vis the Ia antigen than N'Dama cattle, the reverse was the case with the PBM of N'Dama cattle
which expressed more Ia antigens than Boran PBM. Similar results were observed during T. congolense
infection in the two breeds of cattle.
The significantly higher expression of C3bi receptor and correspondingly lower Ia antigen expression
by the PBM of Boran cattle, both during trypanosomosis and in vitro may be responsible for the higher
rate of erythrocyte phagocytosis, hence the development of more severe anaemia by Boran cattle
during trypanosomosis than N'Dama. In addition, the expression of significantly higher numbers of Ia
antigen by N'Dama MΦ, hence are more able to process, present and initiate better trypanosome
antigen-specific immune response than Boran cattle during infection. These two attributes are known
genetic characteristics of trypanotolerance in cattle.
