Expression of IDO in the tumor microenvironment inhibits NK function by downregulation of activating NK receptors DNAM-1, NKp30, NKp44, and NKG2D, inhibition of IFN-γ production, increased IL-4 and IL-13 secretion, and induction of NK cell apoptosis (168–171). The gene discussed is IFNG; the disease is neoplasm.