Human NK cells positively regulate γδ T cells in response to Mycobacterium tuberculosis

The decrease in NK cell activity and the loss of gamma delta T cells in active pulmonary tuberculosis patients have been reported. In this study, we observed that the proliferating response of gamma delta T cells to the heat-treated Ags of Mycobacterium tuberculosis from different individuals was noted to be dependent on the content or function of NK cells in PBMC in a population study. We also found that NK cells were directly rapidly activated by the heat-treated Ags from M. tuberculosis (H37Ra) in vitro; in turn, the activated NK cells improved gamma delta T cell proliferation both by CD54-mediated cell-cell contact through the forming immune synapse and by soluble factors TNF-alpha, GM-CSF, and IL-12, but not IFN-gamma. Our results demonstrated that an interaction between NK cells and gamma delta T cells existed in antituberculosis immunity. Up-regulating the function of NK cells might be beneficial to the prevention and control of pulmonary tuberculosis.