Improvement in MEP purification by combining FLT3 and MPL selection. (A) Schematic of FACS gating for further purifying FLT3⁻ MPB cells into MPL^hi and MPL^lo/− fractions. Representative flow plots with associated FMO controls used to gate for positive and negative populations. (B) Results of dual Mk/E assay showing average colony counts per 100 seeded cells from 3 experiments. The FLT3^-MPL^hi population has the highest Mk/E potential (blue). (C) Methylcellulose assay results showing average CFU-G/M + CFU-GEMM (gray) and BFU-E (red) colony counts per 100 seeded cells for different subpopulations. CFU-G/M + CFU-GEMM (gray) colonies likely arise from CMP contamination in the sorted MEP-enriched population. The FLT3⁻MPL^hi population has the lowest G/M contamination (P = .02 in comparison with FLT3⁻ population).