IFNG and neoplasm: (iii) Impaired secretion of IFN-γ by PI3Kδ−/− CTLs is likely to contribute to defective tumor surveillance [40], given the observation that PI3Kδ regulates IFN-γ production in several lymphocytic lineages [26], [28] and is required for TCR-induced IFN-γ production [39], [41].