title: Human CD34+ CD11b- cord blood stem cells generate in vitro a CD34- CD11b+ subset that is enriched in langerin+ Langerhans dendritic cell precursors.
abstract: OBJECTIVE
  We investigated whether the expression of CD11b on precursors derived in vitro from CD34+ hematopoietic stem cells was related to their ability to generate CD11b- and CD11b+ Langerhans dendritic cells (LC).
  
  
  METHODS
  Human CD34+ cells purified from cord blood were cultured with FLT3 ligand, thrombopoietin, and stem cell factor (FTS) for 2 weeks, analyzed, and sorted by FACS. Sorted fractions were cultured as above, or differentiated into LC with GM-CSF, IL-4, and TGF-beta1 (G4-TGF) for 6 days. The capacity of LC to internalize langerin and dextran was assessed.
  
  
  RESULTS
  Ex vivo, human CD34+ cells were CD11b- and mostly CLA+. After 2 weeks of culture with FTS, CD34- CLA- CD11b- and CD34- CLA- CD11b+ cells emerged. CD11b- cells were the most ancestral because they were the only ones to proliferate with FTS, and constantly generated CD11b+ cells. Both CD11b- and CD11b+ sorted cells generated E-cadherin+ langerin+ LC after incubation with G4-TGF. The former fraction contained 46% +/- 15% of E-cadherin+ and 10% +/- 5% of langerin+ cells, whereas in the latter fraction these values reached respectively 66% +/- 23% and 30% +/- 16% (mean +/- SD, n = 7, p < 0.056). Looking at functional properties, CD11b- and CD11b+ LC were similar in terms of langerin and dextran endocytosis. By contrast, only CD11b+ LC internalized fluorescent LPS.
  
  
  CONCLUSIONS
  Human CD34+ CD11b- cells differentiate in FTS culture into a CD34- CD11b- precursor that in turn generates CD34- CD11b+ cells. These cells are enriched in LC precursors compared to CD34- CD11b- cells. Both CD11b- and CD11b+ LC are generated in vitro, and each fraction may assume different functions in inflammatory situations.
authors.affiliation: Division of Hematology, Geneva University Hospital, Geneva, Switzerland.
authors.forename: Caroline
authors.initials: C
authors.lastname: Soulas
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Arrighi
authors.forename: Sem
authors.initials: S
authors.lastname: Saeland
authors.forename: Bernard
authors.initials: B
authors.lastname: Chapuis
authors.forename: Vincent
authors.initials: V
authors.lastname: Kindler
mesh_terms: D015703:Antigens, CD / Q000096:biosynthesis*; D018952:Antigens, CD34 / Q000096:biosynthesis / Q000276:immunology*; D039481:CD11b Antigen / Q000096:biosynthesis / Q000276:immunology*; D002454:Cell Differentiation / Q000187:drug effects / Q000276:immunology; D002478:Cells, Cultured; D005312:Fetal Blood / Q000166:cytology*; D005434:Flow Cytometry; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000494:pharmacology; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000187:drug effects / Q000276:immunology*; D006801:Humans; D015847:Interleukin-4 / Q000494:pharmacology; D007801:Langerhans Cells / Q000166:cytology / Q000187:drug effects / Q000276:immunology*; D037181:Lectins, C-Type / Q000096:biosynthesis*; D008070:Lipopolysaccharides / Q000494:pharmacology; D037241:Mannose-Binding Lectins / Q000096:biosynthesis*; D008565:Membrane Proteins / Q000494:pharmacology; D019089:Stem Cell Factor / Q000494:pharmacology; D013926:Thrombopoietin / Q000494:pharmacology; D053773:Transforming Growth Factor beta1 / Q000494:pharmacology
chemical_list: D015703:Antigens, CD; D018952:Antigens, CD34; D039481:CD11b Antigen; C121916:CD207 protein, human; D037181:Lectins, C-Type; D008070:Lipopolysaccharides; D037241:Mannose-Binding Lectins; D008565:Membrane Proteins; D019089:Stem Cell Factor; D053773:Transforming Growth Factor beta1; C084881:flt3 ligand protein; D015847:Interleukin-4; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D013926:Thrombopoietin