Restoration of effective erythropoiesis and normal HbA production in xenografts. Representative dot-plots of 3 β2m^null NOD-SCID mice from each group (NBM, TBM, TBM-BGI) 12 to 16 weeks following transplantation. (A) Bone marrow labeled with anti–human CD45 Ab (column 1) showing human cell engraftment and showing apoptotic cells labeled with annexin-V (column 2). (B) Blood from the same mice was labeled with anti–human Ab to glycophorin A (column 3), showing circulating human erythroid cells. Blood also was labeled with anti–human HbAAb (column 4). All samples in columns 1 to 3 were gated on the basis of appropriate isotype controls, and events falling within this gate are shown in dark gray. All events labeled with the respective human antibodies are shown in red. For intracellular HbA staining, anti–human zeta-globin Ab was used as the negative control, and events falling within this gate are shown in dark gray. HbA-labeled events falling outside this gate are shown in red. (C) FACS analysis for HbA on individual human BFUe derived from human progenitors sorted from xenograft bone marrow. The top panel shows representative BFUe's from NBM, TBM, and TBM-BGI xenografts: zeta-globin and HbA expression are shown on the x-axes in columns 1 and 2, respectively. HbA MFI of individual BFUe's derived from different xenografts (NBM n = 20, TBM n = 11, TBM-BGI n = 23) were plotted (bottom panel). MFI of each BFUe is shown on the y-axis. The average HbA MFI of the BFUe's (plotted as a line) was NBM 62 ± 17, TBM 4 ± 1 and TBM-BGI 54 ± 17.