Involvement of gamma delta T cells in immunity to trypanosomiasis

In this study the involvement of peripheral gamma delta T cells, prepared by flow cytometry, in the immune response of cattle to primary infection with Trypanosoma congolense was assessed. Negligible in vitro proliferative responses were observed in gamma delta T cells isolated from trypanosusceptible Boran (Bos indicus) cattle at all stages examined post-infection when stimulated in vitro with parasite antigens. In contrast, both CD8+ T cells and gamma delta T cells from trypanotolerant N'Dama (Bos taurus) cattle proliferated markedly when stimulated in vitro with a complex of invariant trypanosome antigens with MW between 100,000 and 140,000 (100,000 MW complex). Neither species of cattle exhibited significant T-cell recognition of trypanosome variable surface glycoprotein (VSG). To study further the functional and phenotypic characteristics of the gamma delta T-cell response, four T-cell lines were established from infected N'Dama cattle. These cell lines were comprised of up to 96% gamma delta (WC1+) T cells, the remainder being CD8+ T cells. Two of these gamma delta T-cell lines exhibited 100,000 MW complex antigen specificity which was not major histocompatibility complex (MHC) restricted in one line.