Erythropoietic differentiation in humans: in vitro studies on erythroid progenitors and Hb synthesis in fetal, newborn and adult life.

Human erythroid progenitors from fetal liver, cord or adult blood and adult marrow were cultured in methylcellulose, according to standard techniques. Their clonogenetic features (colony morphology and number, time/growth curve, erythropoietin (Ep) and burst-enhancing factor (BEF) sensitivity, in vitro 3H-thymidine suicide index, etc) were comparatively investigated. Three classes of fetal liver erythroid progenitors (primitive or intermediate BFU-E, CFU-E) have been thereby identified and characterized. Furthermore, globin chains (alpha, beta, G gamma, A gamma) synthesis has been evaluated in single erythroid colonies, either well-or poorly-hemoglobinized, by means of a novel technique including analytical iso-electric focusing (IEF), sometimes preceded by preparative IEF separation of HbF and HbA. On the basis of these results, a model for the regulation of Hb synthesis is proposed here.