Lack of adaptation to stromal HLA class I ligands is independent of the HSPC source. HSPCs from adult BM were differentiated to NK cells on 2 MSC lines with divergent HLA-C–encoded KIR ligands. At the indicated time points, the frequency of KIR2DL1 and KIR2DL3 (A), the ratio of KIR2DL1/KIR2DL3 (B), and the frequency of KIR3DL1 (C) were calculated (data are mean and standard deviation of 3 independent experiments).