Mechanism of murine V gamma 1(+) gamma delta T cell-mediated innate immune response against Listeria monocytogenes infection

Murine gammadelta T cells participate in innate immune response against infection of the intracellular bacterium Listeria monocytogenes. In the present report, we analyzed the mechanism of the gammadelta T cell-mediated response against L. monocytogenes infection. gammadelta T cell-enriched spleen cells of L. monocytogenes-infected mice produced IFN-gamma in vitro in response to L. monocytogenes-infected spleen cells, The IFN-gamma production was abrogated by depletion of Vgamma1(+) gammadelta T cells. IFN-gamma production of the Vy1(+) gammadelta T cells in response to L. monocytogenes-infected spleen cells required IL-12. However, addition of Fab fragment of anti-TCR gammadelta monoclonal antibodies (mAb) failed to block the response, suggesting that the response requires no TCR-mediated antigen recognition. Interestingly, Vgamma1(+) gammadelta T cells of naive mice also produced IFN-gamma in response to L. monocytogenes-infected spleen cells in an IL-12-dependent manner. Furthermore, the IL-12 receptor (IL-12R) gene was expressed on the Vgamma1(+) gammadelta T cells of naive mice as well as those of L. monocytogenes-infected mice although naive alphabeta T cells lack IL-12R expression. All the results suggest that the Vgamma1(+) gammadelta T cells participate in immune surveillance against intracellular bacterial infection through quick production of IFN-gamma in response to infection-induced IL-12 without antigen-driven clonal expansion and maturation