Réponse des Lymphocytes T Gamma-Delta à deux Complications de la transplantation rénale (le Cytomégalovirus et les anticorps spécifiques du donneur)

La transplantation rénale est la stratégie de suppléance rénale la plus performante. Le renforcement des thérapeutiques ciblant la réponse cellulaire T (i) a conduit à réévaluer la réponse allogénique humorale et (ii) a souligné deux complications majeures de la pression immunosuppressive : l infection à cytomégalovirus CMV et le risque de cancer. Dans le travail présenté ici, nous analysons d abord l impact histologique de deux de ces facteurs de détérioration de l allogreffon rénal : l infection à CMV avant une biopsie sur indication et la pathogénicité des anticorps anti-HLA dirigés contre le donneur, détectés par des techniques d identification en Single Antigen in situ dans le greffon. Nous montrons ensuite comment les lymphocytes T (LT) g Vd2neg font le lien entre CMV et DSA : induits par le CMV, les LT g Vd2neg participent aux lésions médiées par les DSA par leur capacité à réaliser une lyse dépendante de l anticorps (ADCC) impliquant le CD16. En plus de cette nouvelle fonction allogénique indirecte, les LT g Vd2neg possèdent une double réactivité anti-CMV et anti-tumoral. Nous présentons ici un modèle où les lymphocytes T g V 2neg s activent spécifiquement de façon TCR dépendante par la reconnaissance d un marqueur d intégrité épithéliale (EphA2) : ils détournent le mécanisme d interaction classique d EphA2 avec ses ligands naturels éphrines A1 et A4 pour s en faire un signal de costimulation, en s appuyant sur le contexte de stress pour renforcer son activation. Collectivement, nos résultats contribuent à mieux préciser la bioréactivité et le rôle des LT g V 2neg en transplantation rénale. Nos données suggèrent que chez l'homme, a fortiori lorsqu il est immunodéprimé, les LT g constituent un compartiment de surveillance lymphoide du stress, capable de censurer la dérégulation des cellules infectées ou transformées et de prendre part à la réponse allogénique par un mécanisme d ADCC.Kidney transplant is the most performant strategy for renal replacement therapy. Increasing treatment targetting T cell response has led (i) to reappraise the importance of humoral allogenic response, (ii) to underline two main complications subsequent to immunosuppressive pressure : cytomegalovirus infection and tumorigenesis. Here, we first report the pathological impact of two of these factors on kidney allograft deterioration : CMV infection prior a biopsy for cause and Donor Specific Alloantibodies (DSA) detected within the graft with single antigen flow bead assay. Then we showed that CMV-induced V 2neg g T cells are a new player and a potentially useful clinical biomarker in antibody-mediated lesions of kidney transplants. By engaging DSA on their Fcg-receptor CD16, g T cells participate in allograft lesions mediated by DSA through antibody-dependent cell cytotoxicity (ADCC). In addition to this new indirect allogenic function, CMV-induced V 2neg g T cells displayed a dual anti-CMV and anti-tumor reactivity. Finally, we here identified EphA2 as a new stress-regulated antigen targetting by a non V 2neg g T cell clone, which recognition implies the hijacking of the natural EphA2-ephrin interactions to activation. These data suggest that in humans, a fortiori when immunosuppressed, g T cells compose a lymphoid stress-surveillance compartment, capable of recognizing the dysregulated state of infected or transformed cells and to take part to allogenic response through an ADCC mechanism.BORDEAUX2-Bib. électronique (335229905) / SudocBORDEAUX1-Bib.electronique (335229901) / SudocSudocFranceF

Ab initio Molecular Dynamics in Adaptive Coordinates

We present a new formulation of ab initio molecular dynamics which exploits the efficiency of plane waves in adaptive curvilinear coordinates, and thus provides an accurate treatment of first-row elements. The method is used to perform a molecular dynamics simulation of the CO_2 molecule, and allows to reproduce detailed features of its vibrational spectrum such as the splitting of the Raman sigma+_g mode caused by Fermi resonance. This new approach opens the way to highly accurate ab initio simulations of organic compounds.Comment: 11 pages, 3 PostScript figure

Global ecosystems and fire: multi-model assessment of fire-induced tree cover and carbon storage reduction

In this study, we use simulations from seven global vegetation models to provide the first multi‐model estimate of fire impacts on global tree cover and the carbon cycle under current climate and anthropogenic land use conditions, averaged for the years 2001‐2012. Fire reduces the tree covered area and vegetation carbon storage by 10%. Regionally the effects are much stronger, up to 20% for certain latitudinal bands, and 17% in savanna regions. Global fire effects on total carbon storage and carbon turnover times are lower with the effect on gross primary productivity (GPP) close to zero. We find the strongest impacts of fire in savanna regions. Climatic conditions in regions with the highest burned area differ from regions with highest absolute fire impact, which are characterized by higher precipitation. Our estimates of fire‐induced vegetation change are lower than previous studies. We attribute these differences to different definitions of vegetation change and effects of anthropogenic land use, which were not considered in previous studies and decreases the impact of fire on tree cover. Accounting for fires significantly improves the spatial patterns of simulated tree cover, which demonstrates the need to represent fire in dynamic vegetation models. Based upon comparisons between models and observations, process understanding and representation in models, we assess a higher confidence in the fire impact on tree cover and vegetation carbon compared to GPP, total carbon storage and turnover times. We have higher confidence in the spatial patterns compared to the global totals of the simulated fire impact. As we used an ensemble of state‐of‐the‐art fire models, including effects of land use and the ensemble median or mean compares better to observational datasets than any individual model, we consider the here presented results to be the current best estimate of global fire effects on ecosystems

Electronic Structure Calculation by First Principles for Strongly Correlated Electron Systems

Recent trends of ab initio studies and progress in methodologies for electronic structure calculations of strongly correlated electron systems are discussed. The interest for developing efficient methods is motivated by recent discoveries and characterizations of strongly correlated electron materials and by requirements for understanding mechanisms of intriguing phenomena beyond a single-particle picture. A three-stage scheme is developed as renormalized multi-scale solvers (RMS) utilizing the hierarchical electronic structure in the energy space. It provides us with an ab initio downfolding of the global band structure into low-energy effective models followed by low-energy solvers for the models. The RMS method is illustrated with examples of several materials. In particular, we overview cases such as dynamics of semiconductors, transition metals and its compounds including iron-based superconductors and perovskite oxides, as well as organic conductors of kappa-ET type.Comment: 44 pages including 38 figures, to appear in J. Phys. Soc. Jpn. as an invited review pape

Adult spawning and early larval development of the endangered bivalve Pinna nobilis

[EN] The development of aquaculture activities has posed an alternative solution for the preservation of some overexploited shell¿sh ¿sheries worldwide. In the same way, endemic Mediterranean bivalves such as Pinna nobilis, highly threatened by habitat loss and coastal pollution, could found in aquaculture a solution for preserving the continuity of the species. Given the endangered status of the species, the biological and ecological processes regulating natural populations have been well studied, but there are still important knowledge gaps preventing the development of viable arti¿cial cultures. This study describes for the ¿rst time the larval development of P. nobilis (from fertilization until pediveliger larval stages) in captivity conditions. Moreover, di¿erent rearing tanks of 5, 16 and 80 L, larvae density from 1 to 600 larvae mL¿1, light conditions, food doses, were tested in order to establish the bases for the optimal rearing of the species and provide a source of individuals for restoring ¿eld populations. Results showed that 16 L tanks with a concentration of 2 larvae mL¿1, constant temperature of 21 °C, 12/12 h photoperiod and fed with an ¿optimal¿ mixture of 25 cells per ¿L of Chaetoceros calcitrans + 33.3 cells per¿L ofPavlova lutheri + 100 cells per¿L ofIsochrysis galbana¿ appear to be the best conditions to rearlarvae ofP. nobilis.Di¿erentcaptivity conditions such as loweror highertank volume, larvae density, or food doses; light privation did not report better results for larval development.The present study was financed by the Caisse d'Epargne Cote d'Azur. We are also grateful to the research crew of the Institut Oceanographique Paul Ricard and the Catholic University of Valencia for their technical support and help collecting and maintaining fan mussels. Special thanks to the reviewers for their constructive and necessary suggestions.Trigos, S.; Vicente, N.; Prado, P.; Espinos Gutierrez, FJ. (2018). Adult spawning and early larval development of the endangered bivalve Pinna nobilis. Aquaculture. 483:102-110. doi:10.1016/j.aquaculture.2017.10.015S10211048

Rhizosphere microbiomes of european seagrasses are selected by the plant, but are not species specific

Seagrasses are marine flowering plants growing in soft-body sediments of intertidal and shallow sub-tidal zones. They play an important role in coastal ecosystems by stabilizing sediments, providing food and shelter for animals, and recycling nutrients. Like other plants, seagrasses live intimately with both beneficial and unfavorable microorganisms. Although much is known about the microbiomes of terrestrial plants, little is known about the microbiomes of seagrasses. Here we present the results of a detailed study on the rhizosphere microbiome of seagrass species across the North-eastern Atlantic Ocean: Zostera marina, Zostera noltii, and Cymodocea nodosa. High-resolution amplicon sequencing of 16S rRNA genes showed that the rhizobiomes were significantly different from the bacterial communities of surrounding bulk sediment and seawater. Although we found no significant differences between the rhizobiomes of different seagrass species within the same region, those of seagrasses in different geographical locations differed strongly. These results strongly suggest that the seagrass rhizobiomes are shaped by plant metabolism, but not coevolved with their host. The core rhizobiome of seagrasses includes mostly bacteria involved in the sulfur cycle, thereby highlighting the importance of sulfur-related processes in seagrass ecosystems

The status and challenge of global fire modelling

Biomass burning impacts vegetation dynamics, biogeochemical cycling, atmospheric chemistry, and climate, with sometimes deleterious socio-economic impacts. Under future climate projections it is often expected that the risk of wildfires will increase. Our ability to predict the magnitude and geographic pattern of future fire impacts rests on our ability to model fire regimes, using either well-founded empirical relationships or process-based models with good predictive skill. While a large variety of models exist today, it is still unclear which type of model or degree of complexity is required to model fire adequately at regional to global scales. This is the central question underpinning the creation of the Fire Model Intercomparison Project (FireMIP), an international initiative to compare and evaluate existing global fire models against benchmark data sets for present-day and historical conditions. In this paper we review how fires have been represented in fire-enabled dynamic global vegetation models (DGVMs) and give an overview of the current state of the art in fire-regime modelling. We indicate which challenges still remain in global fire modelling and stress the need for a comprehensive model evaluation and outline what lessons may be learned from FireMIP