IFNG and neoplasm: Two main producers of IFN-γ are natural killer (NK) cells, providing signals from their activating receptors that prevail over signals stemming from inhibitory receptors, and tumor-specific cytotoxic CD8+ T lymphocytes (CTLs) following antigen stimulation of T cell receptor (TCR) or in TCR-independent way that involves synergistic stimulation with cytokines IL-12 and IL-18 [10,11].