Directly after infection, naïve CD4+ T cells activate and differentiate into different subsets of functional T cells, such as IFN-γ-secreting T-helper type 1 (Th1) cells, transforming growth factor-beta 1- (TGF-β1-) secreting T regulatory cells (Tregs), and interleukin- (IL-) 4-secreting Th2 cells [7–9]. This evidence concerns the gene IFNG and infection.