KLRK1 and B-cell chronic lymphocytic leukemia: Several studies have shown that NK cells of CLL patients have a decreased expression of different activating receptors, such as NKp30, NKp46, NKG2D and DNAM-1, compared with healthy donors and that this altered phenotype is accompanied by an impaired cytotoxic activity, degranulation and killing of target cells [37,39,161,162,163,166].