KLRK1 and B-cell chronic lymphocytic leukemia: Concerning activating receptors, the reduced expression of NKG2D, DNAM-1 and natural cytotoxicity receptors (NCRs) reported on NK cells of CLL patients compared to healthy individuals, is paralleled by a defective cytotoxic activity, degranulation and direct killing of target cells (28, 31, 32, 41, 46, 47).