KIR3DL1 and leukemia: Various mechanisms and characteristics could account for this reduced cytotoxicity: (a) an increased expression of MHC class I on leukemic blasts, (b) a reduced expression of ligands of various stimulatory NK cell receptors like NKG2D, NCR, and KIR on leukemic blasts, and (c) a reduced expression of these activating receptors on NK cells of patients with leukemia (Nowbakht et al., 2005; Szczepanski et al., 2010).