KLRK1 and neoplasm: In tumor-bearing mice, the frequency of CD11b+Gr1+ MDSCs inversely correlates with the expression of NK cell-activating receptors including NKG2D and natural cytotoxicity triggering receptor 3 (NCR3, best known as NKp30) on the NK cell surface, as well as with IFNG and PRF1 production [198, 199].