title: Flt3 ligand supports the differentiation of early B cell progenitors in the presence of interleukin-11 and interleukin-7.
abstract: B cell development is influenced by interactions between B cell progenitors and stromal cells. The precise mechanisms by which these interactions regulate B cell differentiation are currently unknown. Flt3 ligand (FL) is a growth factor which stimulates the proliferation of stem cells and early progenitors. Mice deficient for the FLT3 receptor exhibit severe reductions in early B lymphoid progenitors. We have previously described a clonal assay in vitro which allows us to follow the entire B cell differentiation pathway from uncommitted progenitors to mature, immunoglobulin-secreting plasma cells. The growth factor combination of interleukin (IL)-11, mast cell growth factor (MGF) and IL-7 was shown to maintain the differentiation of these hematopoietic precursors into B cell progenitors capable of giving rise to functionally mature B cells in secondary cultures. Here, we show that FL in combination with IL-11 and IL-7 is sufficient to support the differentiation of uncommitted progenitors from day 10 yolk sac (AA4.1+) or day 12 fetal liver (AA4.1+ B220- Mac-1- Sca-1+) into the B lineage. The frequency of B cell progenitors obtained in these conditions was similar, if not better, than the frequency of B cell precursors that arose when cultured in IL-11+MGF+IL-7. Furthermore, the growth factor combination of IL-11+FL+ IL-7 was able to maintain the potential of bipotent precursors giving rise to both the B and myeloid lineages in secondary cultures. We also show that FL synergizes with IL-7 in the proliferation of committed B220+ pro-B cells and may contribute to the maintenance of an earlier pro-B cell population. Together, these results show that FL is important in supporting the differentiation and proliferation of early B cell progenitors in vitro.
authors.affiliation: Wellesley Hospital Research Institute, Toronto, Ontario, Canada. Ray@WHRI.ON.CA
authors.forename: R J
authors.initials: RJ
authors.lastname: Ray
authors.forename: C J
authors.initials: CJ
authors.lastname: Paige
authors.forename: C
authors.initials: C
authors.lastname: Furlonger
authors.forename: S D
authors.initials: SD
authors.lastname: Lyman
authors.forename: R
authors.initials: R
authors.lastname: Rottapel
mesh_terms: D000818:Animals; D016175:B-Lymphocyte Subsets / Q000166:cytology / Q000187:drug effects; D001402:B-Lymphocytes / Q000166:cytology* / Q000187:drug effects* / Q000276:immunology; D002454:Cell Differentiation / Q000187:drug effects / Q000276:immunology; D004357:Drug Synergism; D006412:Hematopoietic Stem Cells / Q000166:cytology* / Q000187:drug effects* / Q000276:immunology; D017370:Interleukin-11 / Q000494:pharmacology*; D015851:Interleukin-7 / Q000494:pharmacology*; D008024:Ligands; D051379:Mice; D008810:Mice, Inbred C57BL; D011518:Proto-Oncogene Proteins / Q000494:pharmacology*; D020794:Receptor Protein-Tyrosine Kinases / Q000494:pharmacology*; D011956:Receptors, Cell Surface / Q000276:immunology / Q000378:metabolism; D019089:Stem Cell Factor / Q000494:pharmacology; D015017:Yolk Sac / Q000166:cytology; D051941:fms-Like Tyrosine Kinase 3
chemical_list: D017370:Interleukin-11; D015851:Interleukin-7; D008024:Ligands; D011518:Proto-Oncogene Proteins; D011956:Receptors, Cell Surface; D019089:Stem Cell Factor; C497971:Flt3 protein, mouse; D020794:Receptor Protein-Tyrosine Kinases; D051941:fms-Like Tyrosine Kinase 3