Studies of Hb F in Adult Nonanemic Baboons: Hb F Expression in Erythroid Colonies Decreases As the Level of Maturation of Erythroid Progenitors Advances

The expression of fetal hemoglobin was studied in erythroid cultures of bone marrow cells from normal baboons using globin biosynthesis and double immunofluorescent labeling with anti-gamma and anti-beta-chain monoclonal antibodies. Baboon erythroid cultures differed from human erythroid cultures in several respects. Erythroid clusters, CFUe, and to a lesser extent BFUe, could be grown without added erythropoietin (Epo), and in vitro maturation time of both CFUe and BFUe was shorter than of their human equivalents. In both CFUe and BFUe cultures Hb F synthesis increased following addition of Epo and reached a plateau at 0.5-1.0 IU. The biosynthetically determined levels of Hb F (mean, SD, and range of gamma/gamma + beta ratios) were: 0.84 +/- 0.09 (0.68-0.89) in BFUe colonies grown in 1.0-2.0 IU of Epo; 0.61 +/- 0.13 (0.45-0.85) in BFUe colonies grown in 0.2 IU of Epo; 0.28 +/- 0.12 (0.21-0.46) in erythroid clusters and CFUe-derived colonies grown at 0.2-0.5 IU of Epo; and 0.04 +/- 0.02 (0.02-0.06) in CFUe colonies and e-clusters grown in the absence of added Epo. Immunofluorescent labeling revealed a pancellular expression of Hb F in all BFUe-derived colonies and bimorphism of Hb F expression in CFUe colonies and in a few erythroid clusters. These results show that, in the baboon, the level of Hb F expression in culture decreases as the presumed differentiative state of cells that produce the erythroid colonies advances.