CD4 and infection: The main function of CD4+ T-cells in immunity against TB is to differentiate into T-helper type 1 (Th-1) effector cells and produce interferon-gamma (IFN-γ), which directly activates macrophages for controlling infection, and TNF-α, which induces apoptosis of macrophages infected with mycobacterium and guides the granuloma formation (4, 24).