FLT3/FLK2 ligand promotes the growth of murine stem cells and the expansion of colony-forming cells and spleen colony-forming units.
The effect of FLT3/FLK2 ligand (FL) on the growth of primitive hematopoietic cells was investigated using ThyloSca1+ stem cells. FL was observed to interact with a variety of factors to initiate colony formation by stem cells. When stem cells were stimulated in liquid culture with FL plus interleukin (IL)-3, IL-6, granulocyte colony-stimulating factor (G-CSF), or stem cell factor (SCF), cells capable of forming colonies in secondary methylcellulose cultures (CFU-c) were produced in high numbers. However, only FL plus IL-6 supported an increase in the number of cells capable of forming colonies in the spleens of irradiated mice (CFU-s). Experiments with accessory cell-depleted bone marrow (Lin- BM) showed that FL alone lacks significant colony-stimulating activity for progenitor cells. Nevertheless, FL enhanced the growth of granulocyte-macrophage progenitors (CFU-GM) in cultures containing SCF, G-CSF, IL-6, or IL-11. In these assays, FL increased the number of CFU-GM initiating colony formation (recruitment), as well as the number of cells per colony (synergy). Many of the colonies were macroscopic and contained greater than 2 x 10(4) granulocytes and macrophages. Therefore, FL appears to function as a potent costimulus for primitive cells of high proliferative potential (HPP). FL was also observed to costimulate the expansion of CFU-GM in liquid cultures of Lin- BM. In contrast, FL had no growth-promoting affects on progenitors committed to the erythrocyte, megakaryocyte, eosinophil, or mast cell lineages.
Hudak
S
S
Department of Immunology, DNAX Research Institute of Molecular and Cellular Biology, Palo Alto, CA 94304, USA.
Hunte
B
B
Culpepper
J
J
Menon
S
S
Hannum
C
C
Thompson-Snipes
L
L
Rennick
D
D
D000818:Animals; D001854:Bone Marrow Cells; D002478:Cells, Cultured; D003114:Colony-Forming Units Assay; D004357:Drug Synergism; D004920:Erythropoiesis / Q000187:drug effects; D006098:Granulocytes / Q000166:cytology; D006410:Hematopoiesis / Q000187:drug effects*; D016298:Hematopoietic Cell Growth Factors / Q000008:administration & dosage* / Q000494:pharmacology; D006412:Hematopoietic Stem Cells / Q000166:cytology*; D066298:In Vitro Techniques; D008565:Membrane Proteins / Q000008:administration & dosage*; D051379:Mice; D008810:Mice, Inbred C57BL; D009000:Monocytes / Q000166:cytology; D011994:Recombinant Proteins; D019089:Stem Cell Factor
D016298:Hematopoietic Cell Growth Factors; D008565:Membrane Proteins; D011994:Recombinant Proteins; D019089:Stem Cell Factor; C084881:flt3 ligand protein