Les progéniteurs multipotents exprimant Flt3 source des précurseurs T extra-thymiques

Les cellules souches hématopoïétiques (CSH) de phénotype LSK (Ligneage-c-Kit+Sca1+) sont à l origine de toutes les lignées sanguines. Leur maturation passe parla génération de progéniteurs multipotents (MPP), subdivisés grâce à l expression deVCAM-1 et Flt3 (VCAM-1+Flt3-: MPP1, VCAM-1+Flt3+: MPP2 et VCAM-1-Flt3+:MPP3). Les MPP3 se différencient en progéniteur lymphoïde commun (CLP), sourcede la lignée B. Sa contribution à la génération de la lignée T reste controversée.La lignée T principale est issue d un progéniteur de la MO qui a colonisé le thymus. Ilexiste aussi une lignée T extra-thymique, identifiés au sein de différents organes(l intestin, la MO, le sang et la rate) dont la maturation se termine dans le thymus oul intestin. Une des questions importantes est de savoir si ces 2 lignées sont issues de lamême source. Nous nous sommes intéressés à la lignée de pré-T extra-thymique (de larate) : Lin-Thy1.2+ CD25+Il7R +. Ces derniers sont très abondants chez la sourisathymique (5-6 fois plus que chez la souris contrôle C57BL/6). Notre but a été dedéfinir la source de cette lignée parmi les progéniteurs de la MO. Suite aux transplantations des différents compartiments hématopoïétiques de la MO àdes receveurs athymiques irradiés, nous avons montré que les MPP3 (VCAM1-Flt3+)sont la population plus douée d activité pré-T. Au contraire, les CLP génèrent deslymphocytes B matures (CD19+IgM+). Ces données sont confortées par l étude del expression de gènes lymphoïdes et myéloïdes qui indique l engagement lymphoïdeprécoce d une sous- population de MPP3. Les cellules progénitrices de la MO quicolonisent la rate (et le thymus) doivent circuler par le sang pour pouvoir coloniser cesorganes. La population de MPP majoritaire en circulation est les MPP3. De plus,l analyse du profil d expression des gènes des récepteurs aux chimiokines et d autresgènes spécifique de la différentiation apporte de nouvelles informations sur le potentielT intrinsèque des progéniteurs de la MO.L ensemble des données accumulées permettent de conclure que les MPP3 sont debons candidats pour la génération des pré-T extra-thymiques et que l engagementlymphoïde commencé dans la MO se termine dans le sang grâce au maintien del expression de Notch1.Pas de résumé en anglaisPARIS5-Bibliotheque electronique (751069902) / SudocSudocFranceF

Early Steps of a Thymic Tumor in SV40 Transgenic Mice: Hyperplasia of Medullary Epithelial Cells and Increased Mature Thymocyte Numbers Disturb Thymic Export

Bone marrow progenitors migrate to the thymus, where they proliferate and differentiate into immunologically competent T cells. In this report we show that mice transgenic for SV40 T and t antigens under the control of the L-pyruvate kinase promoter develop, in a first step, thymic hyperplasia of both thymocytes and epithelial cells. Morphological studies (histology, immunohistolabeling and electron microscopy) revealed modifications of the thymic microenvironment and gradual expansion of medullary epithelial cells in 1 month-old mice, taking over the cortical region. Then, a thymic carcinoma develops. Two-color labeling of frozen sections identified the transgene in medullary epithelial cells. Flow cytometry analysis demonstrated a marked increase in mature CD4+ and CD8+ thymocytes in adult mice (39±10×106 in transgenic mice and 12±5×106 in age-matched controls). Furthermore, thymocyte export was disturbed

Major T Cell Progenitor Activity in Bone Marrow–derived Spleen Colonies

Common lymphoid progenitors (CLP) are generated in adult bone marrow (BM), but the intermediate steps leading to T cell commitment are unknown, and so is the site at which this commitment occurs. Here, we show that colonies arising in the spleen 12 days after BM injection harbor T cell precursors that are undetectable in BM. These precursors did not generate myeloid cells in vivo but repopulated the thymus and the peripheral T cell compartment much faster than did CLP. Two lineage negative (Lin−) subpopulations were distinguished, namely CD44+ Thy1− cells still capable of natural killer generation and transient low-level B cell generation, and T cell–restricted CD44− Thy1+ cells. At a molecular level, frequency of CD3ɛ and preTα mRNA was very different in each subset. Furthermore, only the CD44− Thy1+ subset have initiated rearrangements in the T cell receptor β locus. Thus, this study identifies extramedullary T cell progenitors and will allow easy approach to T cell commitment studies

Treatment of ongoing autoimmune encephalomyelitis with activated B-cell progenitors maturing into regulatory B cells.

The influence of signals perceived by immature B cells during their development in bone marrow on their subsequent functions as mature cells are poorly defined. Here, we show that bone marrow cells transiently stimulated in vivo or in vitro through the Toll-like receptor 9 generate proB cells (CpG-proBs) that interrupt experimental autoimmune encephalomyelitis (EAE) when transferred at the onset of clinical symptoms. Protection requires differentiation of CpG-proBs into mature B cells that home to reactive lymph nodes, where they trap T cells by releasing the CCR7 ligand, CCL19, and to inflamed central nervous system, where they locally limit immunopathogenesis through interleukin-10 production, thereby cooperatively inhibiting ongoing EAE. These data demonstrate that a transient inflammation at the environment, where proB cells develop, is sufficient to confer regulatory functions onto their mature B-cell progeny. In addition, these properties of CpG-proBs open interesting perspectives for cell therapy of autoimmune diseases

Characterization of T Cell Differentiation in the Murine Gut

Gut intraepithelial CD8 T lymphocytes (T-IEL) are distinct from thymus-derived cells and are thought to derive locally from cryptopatch (CP) precursors. The intermediate stages of differentiation between CP and mature T-IEL were not identified, and the local differentiation process was not characterized. We identified and characterized six phenotypically distinct lineage-negative populations in the CP and the gut epithelium: (a) we determined the kinetics of their generation from bone marrow precursors; (b) we quantified CD3-ε, recombination activating gene (Rag)-1, and pre-Tα mRNAs expression at single cell level; (c) we characterized TCR-β, -γ, and -α locus rearrangements; and (d) we studied the impact of different mutations on the local differentiation. These data allowed us to establish a sequence of T cell precursor differentiation in the gut. We also observed that the gut differentiation varied from that of the thymus by a very low frequency of pre-Tα chain mRNA expression, a different kinetics of Rag-1 mRNA expression, and a much higher impact of CD3 ε/δ and pre-Tα deficiencies. Finally, only 3% of CP cells were clearly involved in T cell differentiation, suggesting that these structures may have additional physiological roles in the gut

The European Hematology Association Roadmap for European Hematology Research: a consensus document

The European Hematology Association (EHA) Roadmap for European Hematology Research highlights major achievements in diagnosis and treatment of blood disorders and identifies the greatest unmet clinical and scientific needs in those areas to enable better funded, more focused European hematology research. Initiated by the EHA, around 300 experts contributed to the consensus document, which will help European policy makers, research funders, research organizations, researchers, and patient groups make better informed decisions on hematology research. It also aims to raise public awareness of the burden of blood disorders on European society, which purely in economic terms is estimated at €23 billion per year, a level of cost that is not matched in current European hematology research funding. In recent decades, hematology research has improved our fundamental understanding of the biology of blood disorders, and has improved diagnostics and treatments, sometimes in revolutionary ways. This progress highlights the potential of focused basic research programs such as this EHA Roadmap. The EHA Roadmap identifies nine ‘sections’ in hematology: normal hematopoiesis, malignant lymphoid and myeloid diseases, anemias and related diseases, platelet disorders, blood coagulation and hemostatic disorders, transfusion medicine, infections in hematology, and hematopoietic stem cell transplantation. These sections span 60 smaller groups of diseases or disorders. The EHA Roadmap identifies priorities and needs across the field of hematology, including those to develop targeted therapies based on genomic profiling and chemical biology, to eradicate minimal residual malignant disease, and to develop cellular immunotherapies, combination treatments, gene therapies, hematopoietic stem cell treatments, and treatments that are better tolerated by elderly patients

The European Hematology Association Roadmap for European Hematology Research. A Consensus Document

Abstract The European Hematology Association (EHA) Roadmap for European Hematology Research highlights major achievements in diagnosis and treatment of blood disorders and identifies the greatest unmet clinical and scientific needs in those areas to enable better funded, more focused European hematology research. Initiated by the EHA, around 300 experts contributed to the consensus document, which will help European policy makers, research funders, research organizations, researchers, and patient groups make better informed decisions on hematology research. It also aims to raise public awareness of the burden of blood disorders on European society, which purely in economic terms is estimated at Euro 23 billion per year, a level of cost that is not matched in current European hematology research funding. In recent decades, hematology research has improved our fundamental understanding of the biology of blood disorders, and has improved diagnostics and treatments, sometimes in revolutionary ways. This progress highlights the potential of focused basic research programs such as this EHA Roadmap. The EHA Roadmap identifies nine sections in hematology: normal hematopoiesis, malignant lymphoid and myeloid diseases, anemias and related diseases, platelet disorders, blood coagulation and hemostatic disorders, transfusion medicine, infections in hematology, and hematopoietic stem cell transplantation. These sections span 60 smaller groups of diseases or disorders. The EHA Roadmap identifies priorities and needs across the field of hematology, including those to develop targeted therapies based on genomic profiling and chemical biology, to eradicate minimal residual malignant disease, and to develop cellular immunotherapies, combination treatments, gene therapies, hematopoietic stem cell treatments, and treatments that are better tolerated by elderly patients. Received December 15, 2015. Accepted January 27, 2016. Copyright © 2016, Ferrata Storti Foundatio

Évaluation des organes lymphoïdes au TEP-TDM 18 F-FDG durant le traitement par inhibiteurs de checkpoints immunitaires chez des patients atteints d'un mélanome stade III inopérable ou IV

Background: Immunotherapy (ICI) has revolutionized the management of metastatic melanoma. There is a need to develop robust biomarkers to predict patient response. We studied the lymphoid organs (LO) by 18FDG-PET/CT, and their evolutions to assess their correlation with response, and compared them to 7 clinical and biological markers. Method: This is a retrospective, single-centered, observational study including adult patients with inoperable stage III or IV melanoma under ICIs and followed by a baseline PET/CT (PET0), at 1st (iPET), 3rd (M3PET) and 6th (M6PET) month. We analysed 14 parameters on OLs and tested their inter-observer reproducibility by calculating intra-class correlation coefficients (ICC). The most reproducible ones were used to predict overall survival (OS), and their correlation were assessed with clinical and biological markers. Results: 29 patients were analysed. ICCs>0.90 were observed for 5 parameters. The mean spleen/liver ratio (SLRm) was 0.86. In patients who died at 1 year (1y-OS 1), the SLRm was significantly different at M6PET (p=0.019). In the 1y-OS 0 group, iPET spleen length (SL) increased significantly, compared with PET0 (p=0.014) and M3PET (p=0.0239). Univariable Kaplan-Meier survival analysis found that i%var SL, M3%var SLRm, baseline LDH, i%var NLR and response at M6PET were all predictors of 1y-OS. Conclusion: SLRm could be a prognostic marker in patients with melanoma receiving immunotherapy, its increase being over than 25% at 3 months, compared to baseline, was associated with poor outcome after ICIs.Contexte : l’immunothérapie (ICI) a révolutionné la prise en charge des mélanomes métastatiques. Il est nécessaire de développer des biomarqueurs robustes pour prédire la réponse des patients. Nous avons étudié les organes lymphoïdes (OL) par TEP-TDM au FDG, et leurs évolutions afin de tester leur corrélation avec la réponse, et comparé à 7 marqueurs clinico-biologiques. Méthode : il s’agit d’une étude rétrospective, monocentrique, observationnelle, chez des patients >18 ans, ayant un mélanome stade III inopérable ou IV sous ICIs, suivi par un TEP-TDM au FDG pré-thérapeutique (TEP0), au 1er (iTEP), au 3e (M3) et au 6e (M6) mois. Nous avons analysé 14 paramètres sur les OL, et testé leur reproductibilité inter-observateurs en calculant des coefficients de corrélations intra-classe (ICC). Les plus reproductibles ont été utilisés afin de prédire la survie globale (OS), et leurs corrélations ont été testées avec les marqueurs clinico-biologiques. Résultats : 29 patients ont été analysés. Les ICC >0.90 ont été observés pour 5 paramètres. Le ratio rate/foie moyen (SLRm) était de 0.86. Chez les patients décédés à 1 an (1y-OS 1), le SLRm était significativement différent à M6 (p=0.019). Dans le groupe 1y-OS 0, la flèche splénique (FS) à iTEP augmentait significativement, en comparant avec TEP0 (p=0.014) et M3 (p=0.0239). L’analyse de survie montrait que la variation de la FS à interim, du SLRm à M3, du NLR à iTEP, des LDH à TEP0, et de la réponse à M6 était prédictive de l’OS à 1 an. Conclusion : l’augmentation ≥25% du SLRm à 3 mois, pourrait être un marqueur pronostique chez les patients ayant un mélanome sous immunothérapie, en étant associé à une moins bonne survie globale