Réponses immunitaires et cancer

Publications de l’équipe

Année de publication : 2007

Stéphanie Hugues, Alix Scholer, Alexandre Boissonnas, Alexander Nussbaum, Christophe Combadière, Sebastian Amigorena, Luc Fetler (2007 Jul 31)

Dynamic imaging of chemokine-dependent CD8+ T cell help for CD8+ T cell responses.

Nature immunology : 921-30 En savoir plus
Résumé

Naive T lymphocytes move efficiently in lymphoid tissues while scanning dendritic cells in search of cognate complexes of peptide in major histocompatibility molecules. However, T cell migration ceases after recognition of cognate antigen. We show here that during the initiation of antigen-specific CD8(+) T cell responses, naive CD8(+) polyclonal T cells ‘preferentially’ interacted in an antigen-independent way with mature dendritic cells competent to present antigen to antigen-specific CD8(+) T cells. These antigen-independent interactions required expression of the chemokine receptor CCR5 on polyclonal T cells and increased the efficiency of the induction of naive, low-precursor-frequency CD8(+) T cell responses. Thus, antigen-specific CD8(+) T cells favor the priming of naive CD8(+) T cells by promoting the CCR5-dependent recruitment of polyclonal CD8(+) T cells to mature dendritic cells.

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Elodie Segura, Coralie Guérin, Nancy Hogg, Sebastian Amigorena, Clotilde Théry (2007 Jul 21)

CD8+ dendritic cells use LFA-1 to capture MHC-peptide complexes from exosomes in vivo.

Journal of immunology (Baltimore, Md. : 1950) : 1489-96 En savoir plus
Résumé

Exosomes are secreted vesicles formed in late endocytic compartments. Mature dendritic cells (DCs) secrete exosomes bearing functional MHC-peptide complexes and high levels of ICAM-1. Such exosomes can activate Ag-specific naive T cells but only after recapture by recipient APCs. In this study, we addressed the molecular mechanisms of interaction between exosomes and recipient DCs. We show that exosomes can be presented by mouse DCs without the need for internalization and processing. Exosomes interact with DCs through a specific saturable receptor. Although the two major ligands of ICAM-1, LFA-1 and Mac-1, are expressed by lymphoid organ DCs, only LFA-1 is required for exosome capture by these cells. Accordingly, we show that CD8(+) DCs express higher levels of LFA-1 than CD8(-) DCs, and that they are the main recipients of exosomes in vivo. We propose a new role for LFA-1 on DCs, as a receptor for exosomes to favor Ag transfer between DCs in vivo.

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Alexandre Boissonnas, Luc Fetler, Sebastian Amigorena (2007 Jul 17)

[Stepwise strategy adopted by cytotoxic T cells to eliminate solid tumors].

Médecine sciences : M/S : 570-2 En savoir plus
Résumé

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Carolina Jancic, Ariel Savina, Christina Wasmeier, Tanya Tolmachova, Jamel El-Benna, Pham My-Chan Dang, Steve Pascolo, Maire-Anne Gougerot-Pocidalo, Graça Raposo, Miguel C Seabra, Sebastian Amigorena (2007 Mar 14)

Rab27a regulates phagosomal pH and NADPH oxidase recruitment to dendritic cell phagosomes.

Nature cell biology : 367-78 En savoir plus
Résumé

To prevent excessive degradation of internalized antigens, which could destroy the peptides recognized by T lymphocytes, dendritic cells have developed several strategies that limit proteolytic activity in phagosomes. The recruitment of the NADPH oxidase NOX2 prevents acidification of phagosomes, limiting antigen degradation. Here, we show that dendritic cells derived from Rab27a-deficient ashen mice show increased phagosome acidification and antigen degradation, causing a defect in antigen cross-presentation. Enhanced acidification results from a delay in the recruitment to phagosomes of a subset of lysosome-related organelles containing the membrane subunits of NOX2. The Rab27a-dependent recruitment of these « inhibitory lysosome-related organelles » to phagosomes continuously limits acidification and degradation of ingested particles in dendritic cells, thus promoting antigen cross-presentation.

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Alexandre Boissonnas, Luc Fetler, Ingrid S Zeelenberg, Stéphanie Hugues, Sebastian Amigorena (2007 Jan 31)

In vivo imaging of cytotoxic T cell infiltration and elimination of a solid tumor.

The Journal of experimental medicine : 345-56 En savoir plus
Résumé

Although the immune system evolved to fight infections, it may also attack and destroy solid tumors. In most cases, tumor rejection is initiated by CD8(+) cytotoxic T lymphocytes (CTLs), which infiltrate solid tumors, recognize tumor antigens, and kill tumor cells. We use a combination of two-photon intravital microscopy and immunofluorescence on ordered sequential sections to analyze the infiltration and destruction of solid tumors by CTLs. We show that in the periphery of a thymoma growing subcutaneously, activated CTLs migrate with high instantaneous velocities. The CTLs arrest in close contact to tumor cells expressing their cognate antigen. In regions where most tumor cells are dead, CTLs resume migration, sometimes following collagen fibers or blood vessels. CTLs migrating along blood vessels preferentially adopt an elongated morphology. CTLs also infiltrate tumors in depth, but only when the tumor cells express the cognate CTL antigen. In tumors that do not express the cognate antigen, CTL infiltration is restricted to peripheral regions, and lymphocytes neither stop moving nor kill tumor cells. Antigen expression by tumor cells therefore determines both CTL motility within the tumor and profound tumor infiltration.

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Année de publication : 2006

Francesc Miro, Cinzia Nobile, Nicolas Blanchard, Marianne Lind, Orchidée Filipe-Santos, Claire Fieschi, Ariane Chapgier, Guillaume Vogt, Ludovic de Beaucoudrey, Dinakantha S Kumararatne, Françoise Le Deist, Jean-Laurent Casanova, Sebastian Amigorena, Claire Hivroz (2006 Sep 5)

T cell-dependent activation of dendritic cells requires IL-12 and IFN-gamma signaling in T cells.

Journal of immunology (Baltimore, Md. : 1950) : 3625-34 En savoir plus
Résumé

Patients presenting with genetic deficiencies in IFNGR1, IFNGR2, IL-12B, and IL-12RB1 display increased susceptibility to mycobacterial infections. We analyzed in this group of patients the cross-talk between human CD4+ T lymphocytes and dendritic cells (DCs) that leads to maturation of DC into producers of bioactive IL-12 and to activation of T cells into IFN-gamma producers. We found that this cross-talk is defective in all patients from this group. Unraveling the mechanisms underlying this deficiency, we showed that IL-12 signaling in T cells is required to induce expression of costimulatory molecules and secretion of IL-12 by DCs and that IFNGR expression is required on both DCs and CD4+ T cells to induce IL-12 secretion by DCs. These data suggest that CD4+ T cell-mediated activation of DCs plays a critical role in the defense against mycobacterial infections in humans.

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Ariel Savina, Carolina Jancic, Stephanie Hugues, Pierre Guermonprez, Pablo Vargas, Ivan Cruz Moura, Ana-Maria Lennon-Duménil, Miguel C Seabra, Graça Raposo, Sebastian Amigorena (2006 Jul 15)

NOX2 controls phagosomal pH to regulate antigen processing during crosspresentation by dendritic cells.

Cell : 205-18 En savoir plus
Résumé

To initiate adaptative cytotoxic immune responses, proteolytic peptides derived from phagocytosed antigens are presented by dendritic cells (DCs) to CD8+ T lymphocytes through a process called antigen « crosspresentation. » The partial degradation of antigens mediated by lysosomal proteases in an acidic environment must be tightly controlled to prevent destruction of potential peptides for T cell recognition. We now describe a specialization of the phagocytic pathway of DCs that allows a fine control of antigen processing. The NADPH oxidase NOX2 is recruited to the DC’s early phagosomes and mediates the sustained production of low levels of reactive oxygen species, causing active and maintained alkalinization of the phagosomal lumen. DCs lacking NOX2 show enhanced phagosomal acidification and increased antigen degradation, resulting in impaired crosspresentation. Therefore, NOX2 plays a critical role in conferring DCs the ability to function as specialized phagocytes adapted to process antigens rather than kill pathogens.

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Stephanie Hugues, Alexandre Boissonnas, Sebastian Amigorena, Luc Fetler (2006 Jun 13)

The dynamics of dendritic cell-T cell interactions in priming and tolerance.

Current opinion in immunology : 491-5 En savoir plus
Résumé

Induction of T cell priming and tolerance require direct encounters between naïve T cells and dendritic cells (DCs). T cell activation and proliferation occur in both situations, but the concomitant dynamics of DC-T cell contacts differ: the contacts between naïve T cells and DCs are more stable during the induction of priming than during the induction of tolerance. However, the extent of the differences between the dynamics of the contacts, and the contribution of contact duration and frequency to the functional T cell outcome, remain a matter of debate. Recently, experimental models have been developed to address the role of contact stability in T cell function in vivo, which use real-time imaging of DC-T cell interactions.

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Année de publication : 2005

Luc Fetler, Sebastian Amigorena (2005 Jul 16)

Neuroscience. Brain under surveillance: the microglia patrol.

Science (New York, N.Y.) : 392-3 En savoir plus
Résumé

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Elodie Segura, Sebastian Amigorena, Clotilde Théry (2005 Jul 2)

Mature dendritic cells secrete exosomes with strong ability to induce antigen-specific effector immune responses.

Blood cells, molecules & diseases : 89-93 En savoir plus
Résumé

Exosomes are secreted vesicles formed in late endocytic compartments. Immature dendritic cells (DCs) secrete exosomes which transfer functional MHC-peptide complexes to other DCs. Since immature and mature DCs induce different functional T cell responses (i.e., tolerance versus priming), we asked whether DC maturation also influenced the priming abilities of their exosomes. We show that immature and mature murine DCs secrete morphologically similar exosomes. Extensive proteomic analysis of the two exosome populations showed identical overall protein composition, and provided an exhaustive image of the protein composition of DC-derived exosomes. By quantitative analysis, however, exosomes from mature DCs proved enriched in MHC class II, B7.2, ICAM-1, and depleted in MFG-E8, as compared to immature exosomes. In functional T cell stimulation assays, exosomes secreted by mature DCs were 50- to 100-fold more potent than exosomes from immature DCs, both in vitro and in vivo. MHC class II and ICAM-1 were necessary for the increased immune activity of exosomes secreted by mature DCs. Therefore, changes in protein composition and priming abilities of exosomes reflect the maturation signals received by DCs.

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Philippe Véron, Elodie Segura, Gaël Sugano, Sebastian Amigorena, Clotilde Théry (2005 Jun 29)

Accumulation of MFG-E8/lactadherin on exosomes from immature dendritic cells.

Blood cells, molecules & diseases : 81-8 En savoir plus
Résumé

Exosomes are vesicles of endocytic origin secreted spontaneously by dendritic cells (DCs). We have shown previously that exosomes can transfer antigen or MHC-peptide complexes between DCs, thus potentially amplifying the immune response. We had also identified milk fat globule EGF/factor VIII (MFG-E8), also called lactadherin, as one of the major exosomal proteins. MFG-E8 has two domains: an Arg-Gly-Asp sequence that binds integrins alphavbeta3 and alphavbeta5 (expressed by human DCs and macrophages) and a phosphatidyl-serine (PS) binding sequence through which it associates to PS-containing membranes (among which exosomes). MFG-E8 is thus a good candidate molecule to address exosomes to DCs. Here, we show that MFG-E8 is expressed by immature bone-marrow-derived DCs (BMDCs) and secreted in association with exosomes in vitro. We have generated mice expressing an inactive form of MFG-E8, fused to beta-galactosidase. Analyzing these mice, we demonstrate that MFG-E8 is expressed in vivo in splenic DCs. In a mouse DC-dependent, antigen-specific, CD4 T cell-stimulation assay, exosomes produced by MFG-E8-deficient BMDCs were barely less efficient than exosomes bearing MFG-E8. We conclude that MFG-E8 is efficiently targeted to exosomes but is not essential to address exosomes to mouse BMDCs. Involvement of MFG-E8/lactadherin in exosome targeting to other DC subpopulations, or to human DCs, is still possible.

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Jean-Sébastien Silvestre, Clotilde Théry, Ghislaine Hamard, Jacques Boddaert, Barbara Aguilar, Alain Delcayre, Christophe Houbron, Radia Tamarat, Olivier Blanc-Brude, Sylvia Heeneman, Michel Clergue, Micheline Duriez, Régine Merval, Bernard Lévy, Alain Tedgui, Sebastian Amigorena, Ziad Mallat (2005 Apr 19)

Lactadherin promotes VEGF-dependent neovascularization.

Nature medicine : 499-506 En savoir plus
Résumé

Vascular endothelial growth factor (VEGF)-induced blood vessel growth is involved in both physiological and pathological angiogenesis and requires integrin-mediated signaling. We now show that an integrin-binding protein initially described in milk-fat globule, MFG-E8 (also known as lactadherin), is expressed in and around blood vessels and has a crucial role in VEGF-dependent neovascularization in the adult mouse. Using neutralizing antibodies and lactadherin-deficient animals, we show that lactadherin interacts with alphavbeta3 and alphavbeta5 integrins and alters both VEGF-dependent Akt phosphorylation and neovascularization. In the absence of VEGF, lactadherin administration induced alphavbeta3- and alphavbeta5-dependent Akt phosphorylation in endothelial cells in vitro and strongly improved postischemic neovascularization in vivo. These results show a crucial role for lactadherin in VEGF-dependent neovascularization and identify lactadherin as an important target for the modulation of neovascularization.

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Elodie Segura, Carole Nicco, Bérangère Lombard, Philippe Véron, Graça Raposo, Frédéric Batteux, Sebastian Amigorena, Clotilde Théry (2005 Mar 26)

ICAM-1 on exosomes from mature dendritic cells is critical for efficient naive T-cell priming.

Blood : 216-23 En savoir plus
Résumé

Exosomes are secreted vesicles formed in late endocytic compartments. Immature dendritic cells (DCs) secrete exosomes, which transfer functional major histocompatibility complex (MHC)-peptide complexes to other DCs. Since immature and mature DCs induce different functional T-cell responses (ie, tolerance versus priming), we asked whether DC maturation also influenced the priming abilities of their exosomes. We show that exosomes secreted by lipopolysaccharide (LPS)-treated mature DCs are 50- to 100-fold more potent to induce antigen-specific T-cell activation in vitro than exosomes from immature DCs. In vitro, exosomes from mature DCs transfer to B lymphocytes the ability to prime naive T cells. In vivo, only mature exosomes trigger effector T-cell responses, leading to fast skin graft rejection. Proteomic and biochemical analyses revealed that mature exosomes are enriched in MHC class II, B7.2, intercellular adhesion molecule 1 (ICAM-1), and bear little milk-fat globule-epidermal growth factor-factor VIII (MFG-E8) as compared with immature exosomes. Functional analysis using DC-derived exosomes from knock-out mice showed that MHC class II and ICAM-1 are required for mature exosomes to prime naive T cells, whereas B7.2 and MFG-E8 are dispensable. Therefore, changes in protein composition and priming abilities of exosomes reflect the maturation signals received by DCs.

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Année de publication : 2004

Pierre Guermonprez, Sebastian Amigorena (2004 Dec 14)

Pathways for antigen cross presentation.

Springer seminars in immunopathology : 257-71 En savoir plus
Résumé

Dendritic cells (DCs) have the unique ability to capture cellular tissue antigens, and to present them on MHC class I molecules to antigen-specific CD8(+) T lymphocytes after migration to the draining lymph nodes. This process, called « cross presentation » can lead either to the tolerization or activation of antigen-specific CD8(+) T cells. Antigen capture is believed to occur by phagocytosis of antigen-bearing dead cells. Recent studies suggest that the antigen transferred from the phagocytosed cell to the DC during cross presentation is a proteasome substrate, rather than a proteasomal degradation product. In most cases, the formation of the peptide-MHC class I complexes in DCs requires the export of protein antigens from phagosomes to the cytosol, where they undergo proteasomal degradation. The resulting peptides are then translocated by TAP to the lumen of a cross presentation-loading compartment, for association to MHC class I under the control of chaperones and oxido-reductases. This loading compartment may be either the endoplasmic reticulum (ER) or a mix phagosome-ER compartment. MHC class I egress from the loading compartment to cell surface remains to be analyzed.

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Stéphanie Hugues, Luc Fetler, Laura Bonifaz, Julie Helft, François Amblard, Sebastian Amigorena (2004 Nov 2)

Distinct T cell dynamics in lymph nodes during the induction of tolerance and immunity.

Nature immunology : 1235-42 En savoir plus
Résumé

Induction of immunity and peripheral tolerance requires contacts between antigen-bearing dendritic cells (DCs) and cognate T cells. Using real-time two-photon microscopy, we have analyzed the dynamics of CD8(+) T cells in lymph nodes during the induction of antigen-specific immunity or tolerance. At 15-20 h after the induction of immunity, T cells stopped moving and established prolonged interactions with DCs. In tolerogenic conditions, despite effective initial T cell activation and proliferation, naive T cells remained motile and established serial brief contacts with multiple DCs. Thus, stable DC-T cell interactions occur during the induction of priming, whereas brief contacts may contribute to the induction of T cell tolerance.

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