IFNG and bacterial infectious disease: Abrogation of T-bet-induced IFN-γ production resulted in higher susceptibility to intracellular pathogens in vivo, including Mycobacterium tuberculosis, Leishmania major, and Salmonella typhimurium [18, 60, 61], emphasizing the importance of IFN-γ production by T-bet-expressing Th1 cells in the defense against bacterial infections.