IDO2 and neoplasm: IFN-γ is produced predominantly by activated CD4+ T cells (Th1), CD8+ T cells, γδ T cells, and natural killer (NK) cells and may also demonstrate suppressive effects on anti-tumor immune responses by induction of multiple immunoregulatory factors on tumor cells including indoleamine-2,3-dioxygenase (IDO) and PDL1.