title: The FLK2/FLT3 ligand synergizes with interleukin-7 in promoting stromal-cell-independent expansion and differentiation of human fetal pro-B cells in vitro.
abstract: The effects of a novel cytokine FLK2/FLT3 ligand (FL) on human fetal bone marrow-derived CD34+CD19+ pro-B cells were analyzed in a stromal-cell-independent, serum-deprived culture system. FL, like interleukin-3 (IL-3), synergized with IL-7 in promoting pro-B cell growth, and differentiation of these cells into CD34-CD19+clgM+slgM- pre-B cells, whereas a small proportion of these cells even differentiate into more mature slgM+ B cells. In contrast, KIT ligand (KL) and granulocyte-macrophage colony-stimulating factor (GM-CSF) were ineffective in promoting IL-7-dependent pro-B cell growth and differentiation. Maximal levels of pro-B cell expansion, generally resulting in 15- to 30-fold increases in cellularity, were obtained in cultures supplemented with optimal doses of FL + IL-7 + IL-3. The addition of mouse bone marrow stromal cells further enhanced the proliferation and differentiation of pro-B cells obtained in the presence of these three cytokines. Under these conditions, cultures could be maintained for more than 4 weeks, and in general 40- to 50-fold increases in cell numbers were observed by 3 weeks of culture. The percentages of clgM+ and slgM+ B cells increased 1.5- to 3-fold and 2-fold, respectively, suggesting that stromal cells may provide additional costimulatory signals for human B-cell growth and differentiation that are different from IL-7, IL-3, and FL. Collectively, our results indicate that FL, in contrast to KL, strongly promotes long-term expansion and differentiation of human pro-B cells in the presence of IL-7 or in combination of IL-7 and IL-3, which is a novel property of this hematopoietic growth factor.
authors.affiliation: Human Immunology Department, DNAX Research Institute of Molecular and Cellular Biology, Inc, Palo Alto, CA, USA.
authors.forename: R
authors.initials: R
authors.lastname: Namikawa
authors.forename: M O
authors.initials: MO
authors.lastname: Muench
authors.forename: J E
authors.initials: JE
authors.lastname: de Vries
authors.forename: M G
authors.initials: MG
authors.lastname: Roncarolo
mesh_terms: D000818:Animals; D000944:Antigens, Differentiation, B-Lymphocyte / Q000032:analysis; D001402:B-Lymphocytes; D002454:Cell Differentiation / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D018920:Coculture Techniques; D003238:Connective Tissue / Q000502:physiology; D003239:Connective Tissue Cells; D004357:Drug Synergism; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000494:pharmacology; D006410:Hematopoiesis / Q000187:drug effects*; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000187:drug effects*; D006413:Hematopoietic System / Q000196:embryology; D006801:Humans; D007075:Immunoglobulin M / Q000096:biosynthesis; D007377:Interleukin-3 / Q000494:pharmacology; D015851:Interleukin-7 / Q000494:pharmacology*; D008565:Membrane Proteins / Q000494:pharmacology*; D051379:Mice; D011994:Recombinant Proteins / Q000494:pharmacology; D019089:Stem Cell Factor / Q000494:pharmacology
chemical_list: D000944:Antigens, Differentiation, B-Lymphocyte; D007075:Immunoglobulin M; D007377:Interleukin-3; D015851:Interleukin-7; D008565:Membrane Proteins; D011994:Recombinant Proteins; D019089:Stem Cell Factor; C084881:flt3 ligand protein; D016178:Granulocyte-Macrophage Colony-Stimulating Factor