The most important activating NK cell receptors are; NK gene complex group 2 member D (NKG2D), that binds to molecules of the major histocompatibility complex (MHC) class I related Chain A/B (MICA/B) and UL16 Binding Proteins (ULBP) 1 to 6 on tumor cells; DNAM-1, via binding to CD112 (Nectin-2) and CD155 (also known as poliovirus receptor); and the family members of natural cytotoxicity receptors (NCRs) such as NKp30, NKp44 and NKp46, first identified by Moretta et al. [21]. This evidence concerns the gene KLRK1 and neoplasm.