STEM-CELL FACTOR AND THE AMPLIFICATION OF PROGENITOR CELLS FROM CD34-BLOOD CELLS( CORD)

We have studied the frequency of colony-forming cells (CFC) in fetal a nd neonatal blood in comparison with adult blood and marrow. Fetal or neonatal blood contains at least as many CFC as adult marrow and highe r numbers of the more primitive CFC-those CFC (mixed-cell CFC) giving rise to colonies composed of erythroid and myeloid cells. CD34(+) cord blood cells (selected by one of several means) proliferate in culture over time and generate more CFC (from pre-CFC) and differentiated cel ls in response to stem cell factor (SCF) plus different hematopoietic growth factors. For its effect, SCF requires the synergistic action of erythropoietin (Epo), granulocyte colony-stimulating factor (G-CSF), or interleukin-3 (IL-3). In the presence of Epo or G-CSF, CFC and diff erentiated cells are generated for 15 days and are mainly erythroid or granulocytic, respectively. In contrast, SCF plus IL-3 generate multi lineage CFC and differentiated cells for more than 1 month. When the c onditions for these long-term suspension cultures were optimized, CFC and differentiated cells were generated for more than 2 months. At thi s time, CFC were no longer detectable, but cells continued to be gener ated, and the cells had a mast cell phenotype. These cells have been m aintained and propagated for more than 8 months in the presence of IL- 3 and SCF and may represent a useful tool to study human mast cell dif ferentiation.