Some studies have shown that, compared with healthy people, there is no significant change in the expression of NKG2D on the surface of NK cells in patients with chronic lymphocytic leukemia (CLL) and solid tumors, but the level of soluble NKG2D ligands in serum is higher, which indicates that tumor cells may evade the killing effect mediated by NK cells in the blood and solid tumors by shedding NKG2D ligands from the surface of tumor cells. The gene discussed is KLRK1; the disease is B-cell chronic lymphocytic leukemia.