KIR repertoires do not adapt to stromal HLA class I ligands during NK cell development. Frequency of KIR2DL3 (A) and KIR2DL1 (B) expression during the course of NK cell differentiation of HSPCs from a single CB with KIR A/A genotype on a panel of 5 MSC lines with divergent HLA-C ligands and EL08.1D2. (C) KIR2DL1/KIR2DL3 ratios (mean and standard deviation) of NK cells at week 5 of differentiation of CB-derived HSPCs (n = 3) on EL08.1D2 and the indicated MSC lines. All CB had an A/A KIR genotype. Differences between MSC cultures were nonsignificant by the Fisher t test.