Antigen recognition and immunomodulation by gamma delta T cells in bovine tuberculosis

This report describes the in vitro proliferative responses of peripheral bl ood gamma delta T cells to defined mycobacterial protein Ags and the immuno modulatory effect of gamma delta T cells in cattle infected with Mycobacter ium bovis. gamma delta T cell responses were specific to M. bovis infection because they were detected in cattle either experimentally or naturally in fected with M. bovis, but were not present in uninfected controls. Prolifer ating gamma delta T cell cultures produced enhanced levels of IFN-gamma and TGF-beta, but not IL-2 in response to the more immunodominant mycobacteria l Ags. Depletion of gamma delta T cells from PBMC resulted in an increased Ag-specific proliferation in half the animals tested, indicating a suppress ive effect of gamma delta T cells upon other (alpha beta) T cell responses. Because gamma delta T cells constitute a major T cell population in the pe ripheral blood of cattle, the activities of gamma delta T cells described i n this report could make a significant contribution to the immune response in bovine tuberculosis.