KLRK1 and neoplasm: To address the problem of low or absent NKG2DL expression while still employing the NKG2D receptor for targeted tumor cell-killing, different types of bispecific killer cell engagers were developed, which simultaneously interact with NKG2D and a tumor-associated surface antigen, allowing for NKG2D-positive lymphocytes to attack tumors, independent of NKG2DL recognition [19,20].