In previous studies the IFN-γ+TNFα+CD4+ T cells have been characterized as the major effector memory population needed for protection against infections, among them Leishmania [53,62,63], whereas the earliest single secretion of TNFα and IL-2, followed by double TNFα+IL-2+ producers provides an antigen-specific reservoir of memory CD4+ T cells with effector potential [64,65,66]. This evidence concerns the gene IFNG and infection.