CD4 and tuberculosis: The literature regarding the possible role of polyfunctional CD4+ T cells in mediating vaccine-induced protection for TB has primarily investigated those cells co-producing IFN-γ, TNF-α, and IL-2, hereafter, we will refer to as “polyfunctional CD4+ T cells.” There is substantial evidence derived from study of murine TB models and humans that all three of these cytokines are necessary for the control of Mtb infection.