Antigen Recognition and Immunomodulation by γδ T Cells in Bovine Tuberculosis

Abstract

This report describes the in vitro proliferative responses of peripheral blood γδ T cells to defined mycobacterial protein Ags and the immunomodulatory effect of γδ T cells in cattle infected with Mycobacterium bovis. γδ T cell responses were specific to M. bovis infection because they were detected in cattle either experimentally or naturally infected with M. bovis, but were not present in uninfected controls. Proliferating γδ T cell cultures produced enhanced levels of IFN-γ and TGF-β, but not IL-2 in response to the more immunodominant mycobacterial Ags. Depletion of γδ T cells from PBMC resulted in an increased Ag-specific proliferation in half the animals tested, indicating a suppressive effect of γδ T cells upon other (αβ) T cell responses. Because γδ T cells constitute a major T cell population in the peripheral blood of cattle, the activities of γδ T cells described in this report could make a significant contribution to the immune response in bovine tuberculosis.