title: FLK-2/FLT-3 ligand regulates the growth of early myeloid progenitors isolated from human fetal liver.
abstract: The effects of the recently identified FLK-2/FLT-3 ligand (FL) on the growth of purified human fetal liver progenitors were investigated under serum-deprived culture conditions. FL alone was found to stimulate modest proliferation in short-term cultures of CD34++ CD38+ lineage (Lin)- light-density fetal liver (LDFL) cells and the more primitive CD34++ CD38- Lin- LDFL cells. However, the low levels of growth induced by FL were insufficient for colony formation in clonal cultures. Synergism between FL and either granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin-3 (IL-3) or KIT ligand (KL) was observed in promoting the growth of high-proliferative potential (HPP) colony-forming cells (CF) and/or low-proliferative potential (LPP)-CFC in cultures of CD34++ CD38+ Lin- and CD34++ CD38- Lin- LDFL-cells. FL, alone or in combination with other cytokines, was not found to affect the growth of CD34+ Lin- LDFL cells, the most mature subpopulation of fetal liver progenitors investigated. The growth of the most primitive subset of progenitors studied, CD34++ CD38- Lin- LDFL cells, required the interactions of at least two cytokines, because only very low levels of growth were observed in response to either FL, GM-CSF, IL-3 or KL alone. However, the results of delayed cytokine-addition experiments suggested that individually these cytokines did promote the survival of this early population of progenitors. Although two-factor combinations of FL, KL, and GM-CSF were observed to promote the growth of early progenitors in a synergistic manner, neither of these factors was found to make fetal liver progenitors more responsive to suboptimal concentrations of a second cytokine. Only myeloid cells were recovered from liquid cultures of CD34++ CD38- Lin- LDFL cells grown in the presence of combinations of FL, KL, and GM-CSF. These results indicate that FL is part of a network of growth factors that regulate the growth and survival of early hematopoietic progenitors.
authors.affiliation: Human Immunology and Molecular Biology Departments, DNAX Research Institute, Palo Alto, CA.
authors.forename: M O
authors.initials: MO
authors.lastname: Muench
authors.forename: M G
authors.initials: MG
authors.lastname: Roncarolo
authors.forename: S
authors.initials: S
authors.lastname: Menon
authors.forename: Y
authors.initials: Y
authors.lastname: Xu
authors.forename: R
authors.initials: R
authors.lastname: Kastelein
authors.forename: S
authors.initials: S
authors.lastname: Zurawski
authors.forename: C H
authors.initials: CH
authors.lastname: Hannum
authors.forename: J
authors.initials: J
authors.lastname: Culpepper
authors.forename: F
authors.initials: F
authors.lastname: Lee
authors.forename: R
authors.initials: R
authors.lastname: Namikawa
mesh_terms: D036541:ADP-ribosyl Cyclase; D051997:ADP-ribosyl Cyclase 1; D000818:Animals; D015703:Antigens, CD / Q000032:analysis; D018952:Antigens, CD34; D000943:Antigens, Differentiation / Q000032:analysis; D001483:Base Sequence; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D016895:Culture Media, Serum-Free; D017931:DNA Primers; D005333:Fetus; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000494:pharmacology; D006133:Growth Substances / Q000494:pharmacology*; D016298:Hematopoietic Cell Growth Factors / Q000494:pharmacology; D006801:Humans; D007700:Kinetics; D008099:Liver / Q000166:cytology* / Q000196:embryology; D008562:Membrane Glycoproteins; D051379:Mice; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis / Q000502:physiology*; D020794:Receptor Protein-Tyrosine Kinases / Q000096:biosynthesis / Q000502:physiology*; D011956:Receptors, Cell Surface / Q000502:physiology*; D011994:Recombinant Proteins / Q000494:pharmacology; D019089:Stem Cell Factor; D013234:Stem Cells / Q000166:cytology* / Q000187:drug effects; D051941:fms-Like Tyrosine Kinase 3
chemical_list: D015703:Antigens, CD; D018952:Antigens, CD34; D000943:Antigens, Differentiation; D016895:Culture Media, Serum-Free; D017931:DNA Primers; D006133:Growth Substances; D016298:Hematopoietic Cell Growth Factors; D008562:Membrane Glycoproteins; D011518:Proto-Oncogene Proteins; D011956:Receptors, Cell Surface; D011994:Recombinant Proteins; D019089:Stem Cell Factor; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; C497970:FLT3 protein, human; C497971:Flt3 protein, mouse; D020794:Receptor Protein-Tyrosine Kinases; D051941:fms-Like Tyrosine Kinase 3; D036541:ADP-ribosyl Cyclase; C498154:CD38 protein, human; C498155:Cd38 protein, mouse; D051997:ADP-ribosyl Cyclase 1