KLRK1 and B-cell chronic lymphocytic leukemia: Since the function of CLL-derived NK cells is hampered in settings where activation relies on natural cytotoxicity receptors (and especially NKG2D), we next studied whether this can be explained solely by the reduced expression of activating receptors, that is, NKG2D, or rather whether effector programs are intrinsically affected in CLL-derived NK cells.