Interferon gamma (IFN-γ) is a cytokine that facilitates innate and adaptive immune responses. IFN-γ is secreted by adaptive immune cells, including CD4+ T helper 1 (Th1) cells, CD8+ cytotoxic T cells (CTLs) and natural kills (NK) cells. Other cytokines regulate the expression of IFN-γ and its production can modulate cellular pathways including inflammation, cell proliferation, and cellular differentiation.