Broad Distribution of Colony-Forming Cells with Erythroid, Myeloid, Dendritic Cell, and NK Cell Potential Among CD34++ Fetal Liver Cells

Abstract

The generation of erythroid, myeloid, and lymphoid cells from human fetal liver progenitors was studied in colony-forming cell (CFC) assays. CD38− and CD38+ progenitors that expressed high levels of CD34 were grown in serum-deprived medium supplemented with kit ligand, flk2/flt3 ligand, GM-CSF, c-mpl ligand, erythropoietin, and IL-15. The resulting colonies were individually analyzed by flow cytometry. CD56+ NK cells were detected in 21.9 and 9.9% of colonies grown from CD38− and CD38+ progenitors, respectively. NK cells were detected in mostly large CD14+/CD15+ myeloid colonies that also, in some cases, contained red cells. NK cells were rarely detected in erythroid colonies, suggesting an early split between the erythroid and the NK cell lineages. CD1a+ dendritic cells were also present in three-quarters of the colonies grown from CD38− and CD38+ progenitors. Multilineage colonies containing erythrocytes, myeloid cells, and NK cells were present in 13.7 and 2.7% of colonies grown from CD38− and CD38+ progenitors, respectively. High proliferative-potential CFCs that generated multilineage colonies were also detected among both populations of progenitors. The total number of high proliferative-potential CFCs with erythroid, myeloid, and NK cell potential was estimated to be 2-fold higher in the CD38+ fraction compared with the CD38− fraction because of the higher frequency of CD38+ cells among CD34++ cells. The broad distribution of multipotent CFCs among CD38− and CD38+ progenitors suggests that the segregation of the erythroid, myeloid, and lymphoid lineages may not always be an early event in hemopoiesis. Alternatively, some stem cells may be present among CD38+ cells.