Amplification of the normal erythroid component in β-thalassemic/normal hematopoietic chimeras.

Cohorts of chimeric mice (group 2, n = 9; group 3, n = 11; group 4, n = 11; group 5, n = 6), characterized by a minority component of normal donor HSC engraftment (indicated by the open bars), demonstrated disproportionately large contributions to erythropoiesis from the genetically normal component of the graft as measured by the percentage of its contribution to total Hb in the PB (indicated by the black bars). Group 6 (n = 6) is a cohort of animals chimeric for 2 different distinguishable normal stem cell components; the data for this group represent the stem cell and erythroid contribution from the same donor cells that were used for the genetically normal component in groups 2 through 5. Data represent the mean values and SEM for each group of animals. Normal donor stem cell engraftment and normal donor Hb levels are significantly different from each other (P < .0001) in groups 2, 3, 4, and 5, but are not significantly different in group 6 (P = .11).