We hypothesize that (1) Tregs and MDSCs play important inhibitory roles in M. tb containment, and (2) that Treg cells play a role in HIV latency maintenance. A central scientific premise of this application is that further definition of the immunosuppressive roles of Tregs and MDSCs in TB and HIV infection will reveal important immunopathogenesis mechanisms that may be exploited towards developing improved host-directed therapies (HDTs) for both diseases.