KLRK1 and acute myeloid leukemia: However, several studies have shown that NK cells are defective in AML at the time of diagnosis through the downregulation of activating receptor (e.g., natural cytotoxicity receptor family and NKG2D), upregulation of inhibitory receptors (e.g., KIR and CD94-NKGA), reduction in cytotoxic NK subtypes and impairment in NK maturation [30,31,32].