Characterization of HSPs derived from iPSCs with different HLA genotypes. (A) Expression of A*02:01 and A*24:02 by WT and 6pLOH⁺ iCD34⁺ cells. WT and 6pLOH⁺ iPSCs cultured with OP9 cells for 21 days were examined for HLA-A24 and A2 expression on the gated CD34⁺ cells. (B) HSC induction from WT and 6pLOH⁺ iPSCs and HLA expression by the iCD34⁺ cells. Cultured WT (blue column) and 6pLOH⁺ (red column) with OP9 cells were analyzed for the percentage of CD34⁺ cells and HLA expression by the gated CD34⁺ cells. The data show the mean ± SEM from 3 independent experiments. (C-D) B4002 expression by CD34⁺ cells derived from 3 different iPSCs with different HLA genotypes. iPSCs cultured with a feeder system (OP9 cells) for 21 days were examined for the expression of A2402 and B4002. HSCs derived from a B4002⁻ iPSC clone lacked B4002 but retained A2402 as expected. A representative set of (C) scattergrams and (D) the percentages of CD34⁺ cells and HLA-A allele⁺ cells are shown. The columns represent the mean ± SEM of the values determined by FMC. (E) Hematopoietic colony-forming capacities of iCD34⁺ cells. The pie chart shows CFU, granulocyte, erythrocyte, megakaryocyte, macrophage (CFU-GEMM), CFU-granulocyte (CFU-G), CFU, granulocyte-macrophage (CFU-GM), CFU, macrophage (CFU-M), and burst-forming unit erythroid (BFU-E)–derived colonies generated from the WT-iCD34⁺ cells. (F) The plating efficiencies of iCD34⁺ cells derived from (left panel) 3 WT iPSC clones are compared among (middle panel) 3 different feeder-free systems with StemPro or CM from OP9 or WEHI cells. (Right panel) Summary of the plating efficiencies of iCD34⁺ cells with 3 different HLA genotypes. The data indicate the mean ± SEM of the CFU percentages obtained from 3 independent experiments. The plating efficiency was defined as the frequency of colonies generated from 5000 iCD34⁺ seeded cells (total number of colonies per 5 × 10³ cells seeded). *P < .05; **P < .01; ***P < .001. NS, not significant; SSC-W, side scatter width.