UNIVERSITÉ LIBRE DE BRUXELLES FACULTÉ DES SCIENCES
DÉPARTEMENT DE BIOLOGIE MOLÉCULAIRE LABORATOIRE D’IMMUNOBIOLOGIE
INTRINSIC AND EXTRINSIC CONTROL OF THE PROINFLAMMATORY
CD70/CD27 PATHWAY
THÈSE PRÉSENTÉE PAR MAXIME DHAINAUT
EN VUE DE L’OBTENTION DU TITRE DE DOCTEUR EN SCIENCES
PROMOTRICE : MURIEL MOSER
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TABLE OF CONTENTS
ABBREVIATIONS
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INTRODUCTION
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1. The CD70/CD27 pathway Erreur ! Signet non défini.
2. Regulatory T cells Erreur ! Signet non défini.
2.1. Characterization of suppressor T cells Erreur ! Signet non défini.
2.2. Regulatory T cells in mice : from scurfy to Foxp3 Erreur ! Signet non défini.
2.3. Regulatory T cells in human : the IPEX syndrome Erreur ! Signet non défini.
2.4. The multiple faces of regulatory T cells Erreur ! Signet non défini.
2.
IMMUNOSUPPRESSIVE MECHANISMS OF TREGSERREUR ! SIGNET NON
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3.
TREGS IMPAIR DC FUNCTION
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3.1. Tregs inhibit the development of DC populations Erreur ! Signet non défini.
3.2. Tregs inhibit the migration of DCs to draining lymph nodes Erreur ! Signet non défini.
3.3. Tregs sequester DCs Erreur ! Signet non défini.
3.4. Tregs downregulate the stimulatory capacity of DCs Erreur ! Signet non défini.
3.5. Direct killing of DCs Erreur ! Signet non défini.
4.
CONCLUDING REMARKS
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3. Ectodomain shedding and the regulation of immune responses Erreur ! Signet non défini.
AIM OF THE WORK
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RESULTS AND DISCUSSION
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PART 1: CELL-EXTRINSIC CONTROL OF CD70-DEPENDENT PRIMING BY
REGULATORY T CELLS
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1. Results Erreur ! Signet non défini.
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PART 2: CELL-INTRINSIC CONTROL OF THE CD70/CD27 PATHWAY: A ROLE FOR
CD27 SHEDDING
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1. Results Erreur ! Signet non défini.
2. Discussion Erreur ! Signet non défini.
CONCLUSION
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MATERIALS AND METHODS
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1. Mice Erreur ! Signet non défini.
2. Cell preparation Erreur ! Signet non défini.
3. Immunization protocol and T cell restimulation ex vivo Erreur ! Signet non défini.
4. In vitro assays Erreur ! Signet non défini.
5. Flow cytometry Erreur ! Signet non défini.
6. Quantitative RT-PCR Erreur ! Signet non défini.
7. Retroviral transduction Erreur ! Signet non défini.
8. Supported planar bilayers for study of the immunological synapse Erreur ! Signet non défini.
9. Fluorescence microscopy Erreur ! Signet non défini.
10. Statistical analyses Erreur ! Signet non défini.
REFERENCES
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SUMMARY
A key step in the development of an adaptive immune response is the activation of naive T cells by dendritic cells (DCs). DCs sample antigens in the periphery and migrate to the lymphoid organs were they provide different signals to T cells: they present antigenic peptides in the context of MHC molecules, express costimulatory or coinhibitory ligands and produce cytokines that influence T cell fate. The integration of these signals will either induce tolerance or lead to the activation and expansion of effector T cells which will mediate the immune response.
The costimulatory CD70/CD27 pathway plays important roles in the development of pro-inflammatory Th1 and CTL responses. CD70 expression on DCs has also been described as a molecular switch from tolerance to immunity. Accordingly, its activity is tightly regulated in vivo. The aim of this work was to investigate the mechanisms controlling the expression of CD70 on dendritic cells and CD27 on T lymphocytes.
First, we described a cell-extrinsic mechanism of inhibition exerted on DCs by regulatory T cells (Tregs). Indeed, Tregs controlled Th1 priming in vivo and in vitro by downregulating CD70 on DCs. This control involved a transfer of the CD27 receptor to DCs, possibly via the production of CD27-bearing microvesicles by T cells at the immunological synapse. Acquisition of CD27 by DCs induced the internalization of both CD27 and CD70 and probably their lysosomal degradation. As a consequence, DCs were impaired in their ability to efficiently prime Th1 cells. Second, we analyzed CD70 and CD27 expression in the periphery and provided evidence for a cell-intrinsic control of CD27 expression by ectodomain shedding in the gastrointestinal tract.
While they efficiently clear infections, inflammatory responses can also be deleterious to the organism. By restraining CD70 expression on DCs, Tregs would promote tolerance and limit inflammation. Interestingly, tolerance is particularly important in the intestines, which are in constant contact with dietary antigens and the commensal microbiota. Accordingly, we propose that a second layer of control of CD27-driven costimulation takes place in the gut : by shedding CD27, T cells would be desensitized for any potential CD70-dependent costimulation.