CD4 and HIV-1 infection: This finding has been corroborated by Lalvani and colleagues [90], showing an inverse relationship between plasma levels of Mtb-specific polyfunctional CD4+ T cells that secrete IFN-γ and IL-2 (Figure 3), and HIV-1 viral load, suggesting that HIV-1 infection and Mtb work synergistically to suppress CD4+ T cells.