Alloreactive NK cells at various time points after transplantation. In case no. 11, characterized by C2 KIR-ligand mismatch and no activating KIR, the alloreactive NK cell subset was represented by cells expressing only KIR2DL1. (A) Staining with a mixture of EB6B-PE, DX9-FITC, CH-L-FITC, and Z199 followed by anti-IgG2b-FITC identified alloreactive NK cells, derived from the donor and the recipient (5 months after HSCT), in the top left quadrant (percent is indicated). (B) The specific lysis of BM15 B-EBV cell line expressing the homozygous haplotype HLA-A*0101, -B*4901 (Bw4), -C*0701 (C1) (columns) and the size of alloreactive NK subset (diamonds) were evaluated analyzing the NK cells derived from the donor (◇) and the recipient (♦) at different time points after transplantation. E:T ratio of 20:1 is shown.