Expression of EpoR-tdTomato in subsets of spleen and liver macrophages, BM HSCs, progenitors, megakaryocytes, and B cells. (A) Flow cytometric analysis of EpoR-tdTomato in spleen macrophages. (a) Left panel: representative plot of F4/80 vs forward scatter height (FSC-H) of CD45⁺ cells revealing F4/80⁺ macrophages; right panel: plot of EpoR-tdTomato vs FSC-H of the F4/80⁺ cells revealing EpoR-tdTomato⁺ macrophages. (b) Left panel: representative plot of F4/80 vs CD11b of the CD45⁺ cells; right panel: plot of EpoR-tdTomato vs FSC-H showing the expression of EpoR-tdTomato in the CD11b^High population. (B) Flow cytometric analysis of EpoR-tdTomato in liver macrophages. (a) Left panel: Representative plot of F4/80 vs FSC-H of CD45⁺ cells revealing F4/80⁺ macrophages; right panel: plot of EpoR-tdTomato vs FSC-H of F4/80⁺ cells revealing the EpoR-tdTomato⁺ macrophage population. (b) Left panel: Representative plot of F4/80 vs CD11b of CD45⁺ cells; right panel: plot of EpoR-tdTomato vs FSC-H of F4/80^HighCD11b^Low showing the expression of EpoR-tdTomato in CD11b^High population. (C) western blot analysis of pStat5 of the enriched spleen F4/80⁺ macrophages stimulated with various concentrations of EPO. (D) western blot analysis of pStat5 of the enriched liver F4/80⁺ macrophages stimulated with various concentrations of EPO. (E) Expression of EpoR-tdTomato in HSCs, MPPs, CMPs, MEPs, GMPs, and CLPs. (F) Left panel: representative plot of CD41 vs FSC-H of CD45⁺ cells revealing BM megakaryocytes; right panel: plot of EpoR-tdTomato vs FSC-H of CD41⁺ cells showing the expression of EpoR-tdTomato in subsets of megakaryocytes. (G) Left panel: representative plot of CD19 vs FSC-H of CD45⁺ cells; right panel: plot of EpoR-tdTomato vs FSC-H of B cells showing the expression of EpoR-tdTomato in subsets of B cells. (H) western blot analysis of pStat5 of the sorted BM CD19⁺EpoR-tdTomato⁺ cells stimulated with various concentrations of EPO. N = 3. WT, wild type.