Distribution of CD56^dimand CD56brightNK cells subsets after haploidentical SCT. (A, top) FACS profile of CD3^-CD56^dim (□) and CD3^-CD56^bright (▪) subpopulations of CD3^-CD56⁺ NK cells in 2 patients after haploidentical SCT (no. 8, no. 6), compared with their respective donors. Percentage of NK cells is presented from the engraftment (day 14) to the sixth or fourth month after SCT. Days after transplantation are indicated. (Bottom) Flow cytometric density plots are gated on CD3^-CD56⁺ NK cells at 90 and 180 days after transplantation and are compared with donors. Percentage of CD3^-CD56^dim and CD3^-CD56^bright cells in the total CD3^-CD56⁺ population are indicated. (B, left) Cytotoxicity of CD3^-CD56^bright NK cells compared with CD56^dim NK cells against K562 target cells, for patient no. 8. At engraftment (day 14), all NK cells were CD56^bright (♦). These cells were collected and then activated by 100 IU/mL IL-2 for 8 days. At day 20, PB from the same patient was collected: 80% of circulating NK cells was CD56^bright and 20% was CD56^dim. NK cells collected at day 20 (□) were activated for 2 days with 100 IU/mL IL-2. Cytotoxicity for both NK lines was measured by ⁵¹Cr release assay against K562 target cells. (Right) NK cells from unrelated healthy donor were activated 2 days (□) and 8 days (♦) with 100 IU/mL IL-2 and tested against K562. This result is representative of 2 different experiments.