RAPID COMMUNICATION Recombinant Human Stem Cell Factor Enhances the Formation of Colonies by CD34’ and CD34’lin- Cells, and the Generation of Colony-Forming Cell Progeny From CD34’lin- Cells Cultured With Interleukin-3, Granulocyte Colony-Stimulating Factor, or Granulocyte-Macrophage Colony-Stimulating Factor

We tested the ability of recombinant human stem cell factor (SCF) to stimulate isolated marrow precursor cells to form colonies in semisolid media and to generate colony-forming cells (CFC) in liquid culture. SCF, in combination with interleukin-3 (IL-3), granulocyte-macrophage colony-stimulating factor (GM-CSF), or granulocyte colony-stimulating factor (GCSF) caused CD34+ cells t o form increased numbers of granulocyte-macrophage colonies (CFU-GM), and to form macroscopic erythroid burst-forming units (BFU-E) in the presence of IL-3, erythropoietin (Epo), and SCF. We tested isolated CD34+lincells, a minor subset of CD34’ cells that did not display antigens associated with lymphoid or myeloid lineages, and CD34+lin+ cells, which contain the vast majority of CFC, and found that the enhanced colony growth was most dramatic within the CD34’linpopulation. CD34+lin-