IFNG and hepatitis C virus infection: T cells that produce multiple factors simultaneously (e.g. TNF-α, IL-2 and IFN-γ) are termed polyfunctional T cells and have been shown to provide protection against diseases in murine models of Leishmaniasis and TB [24], [42], control of hepatitis C and HIV-1 infection [28] and possibly vaccine-induced immunity [43], [44].