CIK cell cytotoxic capacity is exerted by the engagement of natural killer group 2 member D (NKG2D) molecules, which recognize specific ligands known as UL16-binding protein family members (ULBP1–6) and MHC class I-related molecules A and B (MIC A/B) widely expressed on tumor cells (39–42). The gene discussed is KLRK1; the disease is neoplasm.