In vitro characteristics of iPSC-PLTs. (A) Representative flow cytometry scatter plots of cell surface A antigen and B antigen expression on JRC-PLTs of types A, B, AB, and O and on iPSC-PLTs. (B) Flow cytometry analysis of JRC-PLTs and iPSC-PLTs of batch 11, 13, 14, 15, 16, and 17. Mean fluorescence intensities (MFI) of CD41, CD42b, CD61, CD36, CD49b, and HLA-A/B/C are shown. For JRC-PLTs, the mean and standard deviation of MFI from 32 individuals are shown. (C) HPA genotypes of patient PBMCs and M35-1 imMKCL, determined using WAKFlow HPA typing reagents. (D) Flow cytometry histogram of iPSC-PLTs and HPA-1a/1a JRC-PLTs using HPA-1a-specific anti-CD61 (clone SZ21) antibody. (E) Scheme of the MR-MAIPA assay to identify HPA-1a antigen expression. (F) Readout ratio of anti–HPA-1a serum to negative control serum for iPSC-PLTs and HPA-1a/1a JRC-PLTs by MR-MAIPA, as in panel C. SZ21 antibody blocks the binding of anti–HPA-1a serum, resulting in values below the cutoff level for JRC-PLTs as well, thereby assuring specificity of the serum. (G) Sizes and percentages of the large IPF corresponding to iPSC-PLTs (batch 18) and blood donor–derived JRC-PLTs at different storage days. Representative data of 3 batches are shown. (H) Representative transmission electron micrograph images of iPSC-PLTs (batch 17) and JRC-PLTs. Scale bar: 1 μm.