Rôle des cellules dendritiques dans le maintien du phénotype endothélial cuboïdal spécialisé dans le recrutement de lymphocytes

Les lymphocytes, cellules effectrices de la réponse immunitaire adaptative, patrouillent dans l'organisme à la recherche d'antigènes étrangers contre lesquels ils sont dirigés. En condition physiologique, ils recirculent continuellement entre la lymphe, le sang, et les organes lymphoïdes secondaires, comme les ganglions lymphatiques. Le transit des lymphocytes naïfs du sang vers le tissu ganglionnaire nécessite une traversée de la paroi vasculaire qui prend place spécifiquement au niveau de veinules post-capillaires: les HEVs (High Endothelial Venules). La lumière de ces vaisseaux sanguins est tapissée de cellules endothéliales cuboïdales exprimant un ensemble de molécules nécessaires au recrutement massif de lymphocytes. En condition physiologique, ce phénotype endothélial hautement différencié est présent exclusivement dans les organes lymphoïdes secondaires, mais peut être induit au sein de tissus subissant une inflammation chronique ou un cancer. Il est donc primordial de comprendre les mécanismes qui régissent l'apparition et le maintien de ce type de vaisseaux afin de pouvoir un jour contrôler l'accès des lymphocytes à un territoire donné. Des études récentes ont mis en évidence un contrôle du phénotype endothélial cuboïdal par le microenvironnement lymphoïde. Néanmoins, les cellules directement impliquées ne sont pas encore caractérisées. Les cellules dendritiques (DC), qui sont amassées autour des HEVs constituaient un bon candidat pour notre étude. Nous avons caractérisé leur rôle grâce à l'utilisation de souris transgéniques CD11c-DTR permettant spécifiquement la déplétion des DCs CD11c+ chez l'adulte suite à l'injection de toxine diphtérique. En absence de DCs, les HEV se dédifférencient pour adopter un phénotype immature similaire à celui observé en période post-natale, provoquant l'abolition de la fonction de recrutement lymphocytaire et une diminution dramatique de la cellularité des ganglions lymphatiques. Nous avons pu suivre en direct ce défaut de recrutement grâce à la technique de microscopie intravitale mettant en évidence des interactions altérées entre les lymphocytes et les veinules du ganglion lymphatique. Des expériences de purification de cellules endothéliales de HEVs et de DCs suivies d'une étape de coculture ont permis de montrer que l'interaction DC/HEV pourrait être directe et impliquer le récepteur LTbetaR exprimé par les HEVs.High Endothelial Venules (HEV) are highly differentiated post-capillary venules specialized in naïve lymphocytes recruitment from the blood. They are located in secondary lymphoid organs and chronic inflammation sites and composed of cuboidal endothelial cells expressing a set of specific molecules allowing them to interact with lymphocytes. Recent studies demonstrate that the lymphoid tissue microenvironment is critical for the maintenance of HEV characteristics, but cell types implicated in this maintenance have not yet been well defined. As dendritic cells (DCs) are drained by lymph flow to lymph nodes where they are found clustered around HEV in the T-cell zone, we addressed the question whether they are responsible for HEV differentiation pressure. Using the CD11c-DTR murine model and bone marrow chimeras, which allow the temporally controlled depletion of all DCs in the mouse, we monitored HEV phenotype and recruitment abilities after various durations of DC depletion. Short term homing assays using naïve fluorescent lymphocytes showed a striking defect of HEV mediated lymphocyte recruitment into lymph node after i.v. injection of cells. Immunofluorescence study of lymph node sections allowed us to observe that HEV topography is highly disturbed and their phenotype is shifted from fully mature adult phenotype to the immature post-natal phenotype. These results, supported by observations of lymphocytes/HEV interactions within the blood flow by intravital microscopy, lead us to conclude that DCs are crucial in the maintenance of HEV phenotype and naïve lymphocyte recruitment into lymph node. Moreover, coculture experiments show that DCs/HEVs interaction could be direct and involve the lymphotoxin-beta receptor on HEV

L’instrumentum en matière dure d’origine animale du site gallo-romain des Bolards (Côte-d’Or) : étude d’une collection ancienne

Cette synthèse, issue d’un travail de Master soutenu à l’Université de Bourgogne, traite d’une collection de 597 objets en matières dures animales récoltés aux Bolards par des collectionneurs privés avant les fouilles officielles. Aujourd’hui conservé au Musée archéologique de Dijon, cet ensemble ne peut être rattaché à la stratigraphie du site ; son analyse passe donc uniquement par son intégration dans une typologie et sa mise en parallèle avec d’autres collections gallo-romaines afin de parvenir à une interprétation et à une datation.This synthesis, drawn from a Master’s thesis realized at the University of Burgundy, concerns the study of 597 osseous artifacts from the site of Les Bolards, amassed by private collectors before the official excavation. Currently kept in the Archaeological Museum of Dijon, this collection cannot be linked to the stratigraphy of the site. Its study therefore consisted only of a typological analysis and comparisons with other Gallo-Roman collections to reach an interpretation and chronological attribution.Der vorliegende Beitrag ist die Synthese einer Masterarbeit, die an der Université de Bourgogne vorgelegt wurde. Sie behandelt einen Korpus von 597 Knochen- und Hirschgeweihartefakten aus dem archäologischen Museum von Dijon, die private Sammler vor den offiziellen Grabungen auf dem Fundplatz Les Bolards in Nuits-Saint-Georges (Departement Côte-d’Or) eingesammelt hatten. Die Artefakte können keiner Stratigraphie des Fundortes zugewiesen werden. Sie können demzufolge nur durch ihre Einordnung in eine Typologie und den Vergleich mit anderen Sammlungen gallo-römischer Artefakte interpretiert und datiert werden

COMPUTER TECHNIQUE IN RAILWAY CONSTRUCTION AND OPERATION

Laboratory mice develop populations of circulating memory CD4+ T cells in the absence of overt infection. We have previously shown that these populations are replenished from naive precursors at high levels throughout life (Gossel et al., 2017). However, the nature, relative importance and timing of the forces generating these cells remain unclear. Here, we tracked the generation of memory CD4+ T cell subsets in mice housed in facilities differing in their 'dirtiness'. We found evidence for sequential naive to central memory to effector memory development, and confirmed that both memory subsets are heterogeneous in their rates of turnover. We also inferred that early exposure to self and environmental antigens establishes persistent memory populations at levels determined largely, although not exclusively, by the dirtiness of the environment. After the first few weeks of life, however, these populations are continuously supplemented by new memory cells at rates that are independent of environment

Management control – International Observatory 2014

International audienc

Intralymphatic CCL21 promotes tissue egress of dendritic cells through afferent lymphatic vessels

To induce adaptive immunity, dendritic cells (DCs) migrate through afferent lymphatic vessels (LVs) to draining lymph nodes (dLNs). This process occurs in several consecutive steps. Upon entry into lymphatic capillaries, DCs first actively crawl into downstream collecting vessels. From there, they are next passively and rapidly transported to the dLN by lymph flow. Here, we describe a role for the chemokine CCL21 in intralymphatic DC crawling. Performing time-lapse imaging in murine skin, we found that blockade of CCL21-but not the absence of lymph flow-completely abolished DC migration from capillaries toward collecting vessels and reduced the ability of intralymphatic DCs to emigrate from skin. Moreover, we found that in vitro low laminar flow established a CCL21 gradient along lymphatic endothelial monolayers, thereby inducing downstream-directed DC migration. These findings reveal a role for intralymphatic CCL21 in promoting DC trafficking to dLNs, through the formation of a flow-induced gradient

ST2 and IL-33 in Pregnancy and Pre-Eclampsia

Normal pregnancy is associated with a mild systemic inflammatory response and an immune bias towards type 2 cytokine production, whereas pre-eclampsia is characterized by a more intense inflammatory response, associated with endothelial dysfunction and a type 1 cytokine dominance. Interleukin (IL)-33 is a newly described member of the IL-1 family, which binds its receptor ST2L to induce type 2 cytokines. A soluble variant of ST2 (sST2) acts as a decoy receptor to regulate the activity of IL-33. In this study circulating IL-33 and sST2 were measured in each trimester of normal pregnancy and in women with pre-eclampsia. While IL-33 did not change throughout normal pregnancy, or between non-pregnant, normal pregnant or pre-eclamptic women, sST2 was significantly altered. sST2 was increased in the third trimester of normal pregnancy (p<0.001) and was further increased in pre-eclampsia (p<0.001). This increase was seen prior to the onset of disease (p<0.01). Pre-eclampsia is a disease caused by placental derived factors, and we show that IL-33 and ST2 can be detected in lysates from both normal and pre-eclampsia placentas. ST2, but not IL-33, was identified on the syncytiotrophoblast layer, whereas IL-33 was expressed on perivascular tissue. In an in vitro placental perfusion model, sST2 was secreted by the placenta into the ‘maternal’ eluate, and placental explants treated with pro-inflammatory cytokines or subjected to hypoxia/reperfusion injury release more sST2, suggesting the origin of at least some of the increased amounts of circulating sST2 in pre-eclamptic women is the placenta. These results suggest that sST2 may play a significant role in pregnancies complicated by pre-eclampsia and increased sST2 could contribute to the type 1 bias seen in this disorder

A novel aspect of the structure of the avian thymic medulla.

We provide evidence for the compartmentalization of the avian thymic medulla and identify the avian thymic dendritic cell. The thymic anlage develops from an epithelial cord of the branchial endoderm. Branches of the cord are separated by primary septae of neural crest origin. The dilation of the primary septae produces the keratin-negative area (KNA) of the thymic medulla and fills the gaps of the keratin-positive network (KPN). Morphometric analysis indicates that the KNA takes up about half of the volume of the thymic medulla, which has reticular connective tissue, like peripheral lymphoid organs. The KNA receives blood vessels and in addition to pericytes, the myoid cells of striated muscle structure occupy this area. The myoid cells are of branchial arch or prechordal plate origin providing indirect evidence for the neural crest origin of the KNA. The marginal epithelial cells of the KPN co-express keratin and vimentin intermediate filaments, which indicate their functional peculiarity. The basal lamina of the primary septum is discontinuous on the surface of the KPN providing histological evidence for the loss of the blood-thymus barrier in the medulla. In the center of the KNA, the dendritic cells lie in close association with blood vessels, whereas the B-cells accumulate along the KPN. The organization of the KPN and KNA increases the "surface" of the so-called cortico-medullary border, thereby contributing to the efficacy of central tolerance

The IL-1-Like Cytokine IL-33 Is Constitutively Expressed in the Nucleus of Endothelial Cells and Epithelial Cells In Vivo: A Novel ‘Alarmin’?

BACKGROUND: Interleukin-33 (IL-33) is an IL-1-like cytokine ligand for the IL-1 receptor-related protein ST2, that activates mast cells and Th2 lymphocytes, and induces production of Th2-associated cytokines in vivo. We initially discovered IL-33 as a nuclear factor (NF-HEV) abundantly expressed in high endothelial venules from lymphoid organs, that associates with chromatin and exhibits transcriptional regulatory properties. This suggested that, similarly to IL-1alpha and chromatin-associated cytokine HMGB1, IL-33 may act as both a cytokine and a nuclear factor. Although the activity of recombinant IL-33 has been well characterized, little is known yet about the expression pattern of endogenous IL-33 in vivo. METHODOLOGY/PRINCIPAL FINDINGS: Here, we show that IL-33 is constitutively and abundantly expressed in normal human tissues. Using a combination of human tissue microarrays and IL-33 monoclonal and polyclonal antibodies, we found that IL-33 is a novel nuclear marker of the endothelium widely expressed along the vascular tree. We observed abundant nuclear expression of IL-33 in endothelial cells from both large and small blood vessels in most normal human tissues, as well as in human tumors. In addition to endothelium, we also found constitutive nuclear expression of IL-33 in fibroblastic reticular cells of lymphoid tissues, and epithelial cells of tissues exposed to the environment, including skin keratinocytes and epithelial cells of the stomach, tonsillar crypts and salivary glands. CONCLUSIONS/SIGNIFICANCE: Together, our results indicate that, unlike inducible cytokines, IL-33 is constitutively expressed in normal human tissues. In addition, they reveal that endothelial cells and epithelial cells constitute major sources of IL-33 in vivo. Based on these findings, we speculate that IL-33 may function, similarly to the prototype 'alarmin' HMGB1, as an endogenous 'danger' signal to alert the immune system after endothelial or epithelial cell damage during trauma or infection

IL-33 Is Produced by Mast Cells and Regulates IgE-Dependent Inflammation

Background: IL-33 is a recently characterized IL-1 family cytokine and found to be expressed in inflammatory diseases, including severe asthma and inflammatory bowl disease. Recombinant IL-33 has been shown to enhance Th2-associated immune responses and potently increase mast cell proliferation and cytokine production. While IL-33 is constitutively expressed in endothelial and epithelial cells, where it may function as a transcriptional regulator, cellular sources of IL-33 and its role in inflammation remain unclear. Methodology/Principal Findings: Here, we identify mast cells as IL-33 producing cells. IgE/antigen activation of bone marrow-derived mast cells or a murine mast cell line (MC/9) significantly enhanced IL-33. Conversely, recombinant IL-33 directly activated mast cells to produce several cytokines including IL-4, IL-5 and IL-6 but not IL-33. We show that expression of IL-33 in response to IgE-activation required calcium and that ionomycin was sufficient to induce IL-33. In vivo, peritoneal mast cells expressed IL-33 and IL-33 levels were significantly lower within the skin of mast cell deficient mice, compared to littermate controls. Local activation of mast cells promotes edema, followed by the recruitment of inflammatory cells. We demonstrate using passive cutaneous anaphylaxis, a mast cell-dependent model, that deficiency in ST2 or antibody blockage of ST2 or IL-33 ablated the late phase inflammatory response but that the immediate phase response was unaffected. IL-33 levels in the skin were significantly elevated only during the late phase