Changes of the phenotype of erythroid progenitor cells (BFU‐E, CFU‐E) and their progenies during early steps of differentiation

Summary. Early differentiation processes of human erythroid progenitor cells (BFU‐e. CFU‐e) have been studied during in vitro proliferation using a panel of monoclonal antibodies with known reactivity on different levels of the erythroid cell line. Two antibodies recognizing structures on BFU‐e (VIP‐2b, BMA 021). two antibodies reactive with CFU‐e and nucleated red cells (5F1, CLB‐Ery‐3) and one antibody directed against glycophorin A (VIE‐G4) were used for this study. Normal human bone marrow cells were induced to proliferation in an erythroid progenitor cell assay and, after different periods of incubation, agar cultures were treated with these antibodies and complement. Thereafter, the remaining erythroid cells were incubated again to continue their proliferation with the same stimulators as before. The changes of the phenotype of BFU‐e and CFU‐e progenies during in vitro proliferation were determined by the reduction of colony formation in comparison with untreated control cultures. Our results indicate that the loss of HLA‐DR antigens and the p45 structure is accompanied by the acquisition of structures recognized by the antibodies 5F1 and CLB‐Ery‐3. After 5–7 d of incubation BFU‐e derived progenies exhibit the same antigenic structure as has been found for CFU‐e. Glycophorin A expression could only be demonstrated at a late differentiation stage of the erythroid cell lineage.