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Published on: September 20, 2013
Human thymic dendritic cell-thymocyte association: ultrastructural cell phenotype analysis
D Landry1, M Lafontaine, H Barthélémy
1Département de Microbiologie, Groupe de Recherche en Immunobiologie de l'Université de Montréal, Québec, Canada.
Insights
Human thymic dendritic cells (DC) form close associations with immature thymocytes in culture. These interactions involve specific cell surface markers, suggesting a role in T-cell development.
Area of Science:
- Immunology
- Cell Biology
- Developmental Biology
Background:
- Associations between dendritic cells (DCs) and thymocytes in the rodent thymus are hypothesized to play a role in T-cell differentiation and maturation.
- Understanding these interactions in humans is crucial for comprehending thymic T-cell development.
Purpose of the Study:
- To investigate and characterize the ultrastructural phenotype of associations between human thymic dendritic cells (DCs) and thymocytes in culture.
- To analyze the cell surface markers of interacting human thymic DCs and thymocytes.
Main Methods:
- Phase contrast microscopy to observe cell interactions.
- Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) for ultrastructural analysis.
- Immunolabeling using monoclonal antibodies and protein A-gold for phenotype characterization.
Main Results:
- Human thymic DCs exhibit long dendrites and bind numerous thymocytes.
- TEM and SEM revealed close membrane contact between DCs and thymocytes.
- Immunolabeling identified two subpopulations of CD1+ DCs (strong and weak).
- Bound thymocytes predominantly expressed CD1, CD4, CD8, and CD2 antigens, with weak CD3 expression, characteristic of immature double-positive thymocytes.
Conclusions:
- Human thymic DCs form intimate associations with CD4+CD8+CD3weak thymocytes in vitro.
- These findings suggest a potential physiological relationship between human thymic DCs and immature thymocytes, warranting further investigation into their role in T-cell development.
Abstract:
In rodent thymus, associations between dendritic cells (DC) and thymocytes have been suggested to be implicated in differentiation and/or maturation processes. In this study, we report intimate associations formed between human thymic DC and thymocytes in culture and we analyze their ultrastructural cell phenotype. Observations by phase contrast microscopy showed that DC present long and thin dendrites and bind many thymocytes. Transmission (TEM) and scanning electron microscopy (SEM) revealed that both cellular populations were in close connection and tight membrane contact could be observed. The phenotype of DC and attached thymocytes was characterized with a series of monoclonal antibodies by protein A-gold TEM and SEM immunolabelings. Quantitative evaluation of immunolabeling (number of gold granules/microns of cellular membrane) suggests the presence of two subpopulations of CD1+ thymic DC (strong and weak), whereas this discrepancy is not observed in DR+ and CD4+ DC populations. On the other hand, the majority of thymocytes bound to DC strongly express the CD1, CD4, CD8 and CD2 antigens and weakly the CD3 antigen, indicating that they represent double-positive immature thymocytes. Uniform distribution of DC and thymocytes membrane antigens was confirmed with a backscattered SEM study. This morphological and immunolabeling TEM and SEM analysis demonstrates that human thymic DC may form associations with CD4+CD8+CD3weak thymocytes and raises questions about their physiological relationship.
