The central scientific premise of this application is that defining the biological mechanisms of the male bias for TB will enlighten our mechanistic understanding of TB pathogenesis and protective human immune responses in TB. A multidisciplinary team with decades of expertise on sex differences (Klein), TB pathogenesis (Bishai), and sex differences in HIV (Scully) will conduct the project. This proposal will investigate the impact of genetics (X chromosome complement) and sex steroid hormones on TB pathogenesis using cellular tools, animal models, and human samples.