Enrichment of peripheral blood RBC chimerism compared with RBCprogenitor chimerism in the bone marrow and spleen. Early RBC progenitors (defined as Ter-119^high/CD71^high/pan-CD45⁺/PI^-) were quantified by flow cytometry, and their origin (donor, eGFP⁺/CD45.1^-) or host (eGFP^-/CD45.1⁺) was determined. In both bone marrow (A) and spleen (B), sickle RBC progenitors predominated despite near complete replacement of the peripheral blood with donor RBCs. The x-axis shows the percentage of donor Hb in the peripheral blood. The y-axis depicts the percentage of eGFP⁺/CD45.1^- donor (▴) or eGFP^-/CD45.1⁺ sickle (▴) RBC progenitors in individual mice receiving transplants. In sickle (0% donor Hb) or eGFP (100% donor Hb) control animals the percentage of donor (•) or host (▵) RBC progenitors is also shown.