Human CD34+CD11b− cord blood stem cells generate in vitro a CD34−CD11b+ subset that is enriched in langerin+ Langerhans dendritic cell precursors
Received 13 April 2006; received in revised form 9 June 2006; accepted 14 June 2006.
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-β1 (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.
Conclusion
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.
aDivision of Hematology, Geneva University Hospital, Geneva, Switzerland
bDepartment of Dermatology, Geneva University Hospital, Geneva, Switzerland
cSchering Plough, Laboratory of Immunological Research, Dardilly, France
Offprint requests to: Vincent Kindler, Ph.D., P.D., Division of Hematology, Geneva University Hospital, 25, Micheli-du-Crest, 1211 Geneva 14, Switzerland
ABSTRACT