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Isolation of Myeloid Dendritic Cells and Epithelial Cells from Human Thymus
Published on: September 20, 2013
Functional and phenotypic analysis of thymic CD34+CD1a- progenitor-derived dendritic cells: predominance of CD1a+
A H Dalloul1, C Patry, J Salamero
1Laboratoire d'Immunologie Cellulaire, Unité Mixte de Recherche 7627, Centre National de la Recherche Scientifique, Hôpital Pitié-Salpêtrière, Paris, France. dalloul@ccr.jussieu.fr
Insights
Human thymic progenitors differentiate into dendritic cells (DC) via a CD1a+ pathway, distinct from monocyte-derived DC. Granulocyte-macrophage colony-stimulating factor (GM-CSF) aids, but is not essential for, this differentiation process.
Area of Science:
- Immunology
- Cell Biology
Background:
- Dendritic cells (DC) are crucial for immune responses, with distinct subsets originating from different lineages.
- Thymic DC play a vital role in eliminating autoreactive T cells, raising questions about their unique characteristics compared to monocyte-derived DC.
- The specific cytokine requirements for differentiating DC from thymic progenitors remain incompletely understood, particularly the role of GM-CSF.
Purpose of the Study:
- To investigate the differentiation pathways of human thymic progenitors into DC.
- To compare thymic DC with monocyte-derived DC regarding phenotype, function, and cytokine requirements.
- To elucidate the role of specific cytokines like GM-CSF and M-CSF in DC differentiation.
Main Methods:
- Differentiation of CD34+ thymic progenitor cells using various cytokine combinations.
- Phenotypic analysis of generated DC using markers like CD1a and CD14.
- Functional assessment of DC, including mixed lymphocyte reaction (MLR) induction.
- Study of MHC class II trafficking via metabolic labeling and immunoprecipitation.
Main Results:
- Thymic progenitors differentiated into DC with various cytokine combinations, with IL-7 being essential and GM-CSF improving yield.
- CD14+ monocytic intermediates were observed only with M-CSF addition, and these cells could differentiate into CD1a+ DC.
- Thymic-derived CD1a+ DC and monocyte-derived DC exhibited similar Ag-processing machinery and MHC class II trafficking.
- TNF-alpha accelerated DC differentiation and enhanced MHC class II presentation, improving MLR capacity.
Conclusions:
- Human thymic progenitors can differentiate into DC along a preferential CD1a+ pathway.
- Thymic DC retain a CD14+ maturation capacity under M-CSF, indicating conserved differentiation potential.
- Despite distinct origins, thymic-derived and monocyte-derived DC share significant functional similarities in antigen processing.
Abstract:
Whether thymic dendritic cells (DC) are phenotypically and functionally distinct from the monocyte lineage DC is an important question. Human thymic progenitors differentiate into T, NK, and DC. The latter induce clonal deletion of autoreactive thymocytes and therefore might be different from their monocyte-derived counterparts. The cytokines needed for the differentiation of DC from thymic progenitors were also questioned, particularly the need for GM-CSF. We show that various cytokine combinations with or without GM-CSF generated DC from CD34+CD1a- but not from CD34+CD1a+ thymocytes. CD34+ thymic cells generated far fewer DC than their counterparts from the cord blood. The requirement for IL-7 was strict whereas GM-CSF was dispensable but nonetheless improved the yield of DC. CD14+ monocytic intermediates were not detected in these cultures unless macrophage-CSF (M-CSF) was added. Cultures in M-CSF generated CD14-CD1a+ DC precursors but also CD14+CD1a- cells. When sorted and recultured in GM-CSF, CD14+ cells down-regulated CD14 and up-regulated CD1a. TNF-alpha accelerated the differentiation of progenitors into DC and augmented MHC class II transport to the membrane, resulting in improved capacity to induce MLR. The trafficking of MHC class II molecules was studied by metabolic labeling and immunoprecipitation. MHC class II molecules were transported to the membrane in association with invariant chain isoforms in CD14+ (monocyte)-derived and in CD1a+ thymic-derived DC but not in monocytes. Thus, thymic progenitors can differentiate into DC along a preferential CD1a+ pathway but have conserved a CD14+ maturation capacity under M-CSF. Finally, CD1a+-derived thymic DC and monocyte-derived DC share very close Ag-processing machinery.
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