TNF and cytomegalovirus infection: Indeed, upon HCMV infections/reactivations, CD56dim NK cells acquire a mature NKG2Cpos/CD57pos/NKG2Aneg/KIRpos phenotype, thus becoming fully licensed to efficiently exert anti-viral and anti-tumor properties (i.e., production of IFN-γ and Tumor Necrosis Factor (TNF)-α) (167–169).