IFN-gamma (Interferon-gamma) is a dimerized soluble cytokine that is the only member of the type II class of interferons. It is the prototype proinflammatory cytokine and is produced by a variety of immune cells under inflammatory conditions, notably by T cells and NK cells. A primary role for IFN-γ is the activation of macrophages to increase phagocytosis, tumoricidal properties, and intracellular killing of pathogens, particularly bacteria and fungi. IFN-gamma dimers signal through a receptor complex of two IFN-gamma R1 and two IFN-gamma R2 subunits. The R1 chain is sufficient for binding, but the R2 chain is required for signaling and receptor complex formation.