IFNG and neoplasm: On the basis of the surface antigen expression, two major NK cell subsets can be distinguished: CD56dimCD16+ NKs (90–95% of total circulating NKs), able to produce perforin and granzymes and that mediate the ADCC; and CD56brightCD16- NKs (5–10% of total circulating NKs), able to release anti-tumor Th1 cytokines, such as IFNγ and TNFα [25,26].