IFNG and Salmonella Infections: Also, in granulomas formed in response to Leishmania major infection, iNOS expression does not require direct interaction between APC and CD4+ T cells (51), which means that IFN-γ can still induce iNOS expression even if CD4+ T cells are not directly interacting with the granuloma-forming cells; therefore, failure to control Salmonella infection in T-bet−/− mice is not related to an inability of CD4+ T cells to migrate to infected tissues.