title: Human primitive hematopoietic progenitor cells are more enriched in KITlow cells than in KIThigh cells.
abstract: To clarify the phenotypes of various classes of human hematopoietic progenitor cells, we used a multicolor staining protocol in conjunction with CD34 and a newly developed mouse antihuman c-kit proto-oncogene product (KIT) monoclonal antibody (MoAb). We characterized three cell fractions in CD34+ cells that express KITlow and KIThigh cells in addition to KIT- cells. A clonogenic assay showed that most granulocyte-macrophage colony-forming cells (GM-CFC) were present in CD34+KIThigh populations, whereas erythroid burst-forming cells (BFU-E) were detected mainly in the CD34+KITlow population. CD34(+)-KIT- fraction contained a small number of BFU-E. Morphologic analysis showed that blast-like cells were more enriched in the CD34+KITlow fraction. KITlow cells contained CD34+CD38- cells that were considered to be very primitive progenitor cells, as determined by a replating assay. To clarify the biologic differences between both fractions, we examined the more primitive progenitor cell functions by assessing long-term culture-initiating cells (LTC-IC) on the stromal cells. At week 2, more CFC recovered from the culture in the fraction initiated with a CD34+KIThigh population. However, more LTC-IC were present during weeks 5 to 9 in the CD34+KITlow population. These results indicate that primitive progenitors are more enriched in the KITlow population and that the KIThigh population contains many GM-committed progenitor cells. We also showed that anti-KIT MoAb inhibited the ability of CD34+ cells to generate CFC on the stromal layer in the LTC system. This suppressive effect was more evident in the generation of BFU-E by CD34+KITlow cells. Moreover, we confirmed that CD34+KIThigh cells emerged from CD34+KITlow cells during coculture with allogeneic stromal cells or from liquid culture in the presence of stem cell factor (SCF), interleukin-6, and erythropoietin. These results emphasize the pivotal role of the KIT and SCF interaction in hematopoiesis and indicate that KITlow cells are more primitive than KIThigh cells.
authors.affiliation: Department of Pediatrics and Medicine, Jichi Medical School, Tochigi-ken, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Gunji
authors.forename: M
authors.initials: M
authors.lastname: Nakamura
authors.forename: H
authors.initials: H
authors.lastname: Osawa
authors.forename: K
authors.initials: K
authors.lastname: Nagayoshi
authors.forename: H
authors.initials: H
authors.lastname: Nakauchi
authors.forename: Y
authors.initials: Y
authors.lastname: Miura
authors.forename: M
authors.initials: M
authors.lastname: Yanagisawa
authors.forename: T
authors.initials: T
authors.lastname: Suda
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D015703:Antigens, CD / Q000032:analysis; D018952:Antigens, CD34; D002469:Cell Separation; D002478:Cells, Cultured; D006410:Hematopoiesis; D006412:Hematopoietic Stem Cells / Q000737:chemistry*; D006801:Humans; D051379:Mice; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins / Q000032:analysis* / Q000276:immunology; D019009:Proto-Oncogene Proteins c-kit; D020794:Receptor Protein-Tyrosine Kinases / Q000032:analysis* / Q000276:immunology; D016184:Receptors, Colony-Stimulating Factor / Q000032:analysis* / Q000276:immunology
chemical_list: D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D018952:Antigens, CD34; C000715470:MAS1 protein, human; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins; D016184:Receptors, Colony-Stimulating Factor; D019009:Proto-Oncogene Proteins c-kit; D020794:Receptor Protein-Tyrosine Kinases