KLRK1 and acute myeloid leukemia: Analysis of the expression of the activating receptor NKG2D on NK cells and its ligands (MHC class I chain-related (MIC) A/B and UL16 binding proteins (ULBPs)), which are down-regulated or absent on AML cells [32], [44]-[46], could also provide a possible explanation for the improved sensitivity towards NK cells.