KIR2DL1 and osteosarcoma: The osteosarcoma cell line lacking expression of HLA-C group 1 and 2 was efficiently lysed by NK cells from 2 donors lacking expression of KIR2DL1 or 3 major inhibitory KIRs (KIR2DL1, KIR2DL2/3, and KIR3DL1), respectively.