Analysis of erythropoiesis by erythroid colony formation in culture

The development of clonal assays for hemopoietic progenitors has provided new tools for the analysis of normal and abnormal cell regulation. Such assays have been applied to erythropoiesis and have demonstrated classes of precursors which differ significantly in their growth potential, physical characteristics, and sensitivity to the hormone, erythropoietin. A formal geneology of these classes has been established and insight into the factors that regulate the numbers of the classes provided by studies in anemic and polycythemic animals. The results suggest that commitment to the earliest erythroid progenitors recognizable in culture is not controlled by erythropoietin, whereas the most differentiated elements demonstrate a requirement for the hormone for their maintenance. Recognition of differences in the factors that control erythroid differentiation predict that a variety of mechanisms will be found to account for different forms of erythroid failure in man.