KIR2DL2/3 recognize both C1 and C2 groups of alleles. Case no. 6 was characterized by C1 KIR-ligand mismatch, because the patient expressed HLA-A*1101,*3202, -B*3508,*1517 (Bw6/Bw4), -C*1504,*1602 (C2/C2), while the donor expressed HLA-A*33,*32, -B*14,*15 (Bw6/Bw4), -C*0802,*1602 (C1/C2). (A) Polyclonal activated NK cells derived at the third month after transplantation were tested for cytolytic activity against patient's leukemia blasts (JMML; ■) and the B-EBV BOB (□) in the absence and presence of mAb to the indicated molecules, such as 11PB6 (KIR2DL1/S1), GL-183 (KIR2DL2/L3/S2), and A6-136 (HLA-class I). The E:T ratio used was 10:1. The representative KIR2DL1/S1⁻ KIR2DL2/3⁺ 6R-30 (B) and 6R-14 (C) clones were tested against 221/Cw3 and 221/Cw4 cell transfectants in the absence (□) and in the presence of the anti-KIR2DL2/3 () CH-L mAb, or the anti–HLA-class I (■) 6A4 (in case of Cw4 transfectant) or A6-136 mAb (in case of Cw3 transfectant). The E:T ratio used was 5:1. (D) 721.221 cells transfected with HLA-Cw6 or -Cw7 were stained with either W6/32 anti–HLA-class I mAb or with KIR2DL2-Fc, KIR2DL3-Fc soluble receptors. Empty profiles indicate staining with second reagent alone. Numbers within histograms indicate MRFI.