CD4 and tuberculosis: The major mechanisms of cell-mediated immunity include CD4 Th1-cell mediated activation of macrophages to destroy intracellular bacterial pathogens, and the central role of IFN-γ in the control of tuberculosis has been clearly demonstrated by the susceptibility to mycobacterial infections in mice with a disrupted IFN-γ gene and in humans with mutations in genes involved in the IFN-γ and IL-12 pathways [1]–[4].Unlike CD4 T cells, which are crucial in the defence against M.tb, the role of CD8 T cells is not fully resolved.