CD4 and tuberculosis: Chackerian, et al. [20] also found increased numbers of IFN-γ-producing CD4+ T cells in the lungs of sst1-resisitant C57BL/6 inbred mice, and conjectured that TB susceptibility was related to the ability to recruit mycobacteria-specific IFN-γ-producing Th1 cells to the lungs.