Long-term outcomes after reduced-intensity conditioning allogeneic stem cell transplantation for low-grade lymphoma: a survey by the French Society of Bone Marrow Graft Transplantation and Cellular Therapy (SFGM-TC).

International audienceBACKGROUND AND OBJECTIVES: High-dose chemotherapy with allogeneic stem cell transplantation (SCT) has proven to be a successful treatment for low-grade lymphoma (LGL), but is associated with considerable transplant-related mortality (TRM). In an effort to reduce toxic mortality while maintaining the graft-versus-leukemia effect, allogeneic SCT has been combined with a reduced-intensity conditioning (RIC) regimen. The aim of this study was to determine the outcome of patients with LGL treated with RIC allogeneic SCT. DESIGN AND METHODS: This retrospective multicenter study included 73 patients with relapsed or refractory LGL allografted after a RIC regimen between 1998 and 2005 whose data were recorded in a French registry. RESULTS: Patients received a median of three lines of therapy prior to RIC allogeneic SCT. The most widely used conditioning regimens were fludarabine + busulfan + antithymocyte globulin (n=43) and fludarabine + total body irradiation (n=21). Prior to allografting, patients were in complete response (CR; n=21), partial response (PR; n=33) or had chemoresistant disease (n=19). The median follow-up was 37 months (range, 16 to 77 months). In patients in CR, PR and chemoresistant disease, the 3-year overall survival rates were 66%, 64% and 32%, respectively, while the 3-year event-free survival rates were 66%, 52% and 32%, respectively. The 3-year cumulative incidences of TRM were 32%, 28% and 63%, respectively. The incidence of relapse was 9.6%. INTERPRETATION AND CONCLUSIONS: Although associated with significant TRM, RIC allogeneic SCT in advanced chemosensitive disease leads to long-term survival

STAT5-and hypoxia-dependent upregulation of AXL

Internal tandem duplication in Fms-like tyrosine kinase 3 (FLT3-ITD) is the most frequent mutation observed in acute myeloid leukemia (AML) and correlates with poor prognosis. FLT3 tyrosine kinase inhibitors are promising for targeted therapy. Here, we investigated mechanisms dampening the response to the FLT3 inhibitor quizartinib, which is specific to the hematopoietic niche. Using AML primary samples and cell lines, we demonstrate that convergent signals from the hematopoietic microenvironment drive FLT3-ITD cell resistance to quizartinib through the expression and activation of the tyrosine kinase receptor AXL. Indeed, cytokines sustained phosphorylation of the transcription factor STAT5 in quizartinib-treated cells, which enhanced AXL expression by direct binding of a conserved motif in its genomic sequence. Likewise, hypoxia, another well-known hematopoietic niche hallmark, also enhanced AXL expression. Finally, in a xenograft mouse model, inhibition of AXL significantly increased the response of FLT3-ITD cells to quizartinib exclusively within a bone marrow environment. These data highlight a new bypass mechanism specific to the hematopoietic niche that hampers the response to quizartinib through combined upregulation of AXL activity. Targeting this signaling offers the prospect of a new therapy to eradicate resistant FLT3-ITD leukemic cells hidden within their specific microenvironment, thereby preventing relapses from FLT3-ITD clones

EXPRESSION DE LA NEUROPILINE-1 DANS LES LYMPHOCYTES T CONVENTIONNELS ET « INVARIANT NATURAL KILLER T » (iNKT) MURINS

Neuropilin-1 (Nrp-1) is a one way transmembrane protein originally identified as a receptor for both axonal guidance cues (class 3 semaphorins, Sema3) and angiogenic factors (vascular endothelial growth factor, VEGF). In addition to its role in the development of the nervous and cardiovascular systems, Nrp-1 has been attributed critical functions in numerous adult physiological and pathological processes following the binding of old (Sema3 and VEGF) and new (TGF-β and PDGF) ligands. In the immune system, Nrp-1 participates in the immune synapse between T cells and dendritic cells, acts as a coreceptor for the immunoregulatory Sema3A on T cells, and is involved in the suppressive functions of murine Foxp3+ regulatory T (Treg) cells. However, little is known about Nrp-1 expression in human and murine non-Treg T cells. The aim of this project was to characterize non-Treg Nrp-1+ T cell populations in mice, analyze their functions, identify the mechanisms leading to Nrp-1 expression in these cells, and understand the role of Nrp-1 in T cell responses. On the one hand, I have studied a population of unconventional innate-like T cells named invariant natural killer T (iNKT) cells. iNKT cells are thymus-derived CD1d-reactive αβ T cells with potent immunomodulatory properties based on their quick release of both TH1 and TH2 cytokines after TCR triggering. A distinct subset of iNKT cells, whose origin and homeostasis are still poorly understood, produces the pro-inflammatory cytokine IL-17. In the present study, I have found that IL-17-producing iNKT cells are part of the recent thymic emigrant iNKT cell pool, which can be unequivocally identified as Nrp-1+ iNKT cells in peripheral lymphoid organs of naive mice. On the other hand, I have analyzed Nrp-1 expression in conventional non-Treg αβ T cells. In naive mice, Nrp-1 is expressed on proliferating immature thymocytes and memory phenotype mature T cells with an increased homeostatic proliferation rate. In vitro experiments have shown that Nrp-1 expression is induced in T cells by TCR activation in a Ca2+/calcineurin/NFAT signaling pathway-dependent manner. Nrp-1 expression in activated T cells sensitizes them to the regulatory effects of its ligands Sema3A and TGF-β1. In conclusion, the results presented here provide original data on Nrp-1 expression and function in the immune system. More generally, this study paves the way for further basic and translational research on Nrp-1-mediated processes in immune-related diseases, cancer, and neurological disorders.La neuropiline-1 (Nrp-1) est une protéine transmembranaire agissant comme récepteur des sémaphorines de classe 3 (Sema3) et du facteur de croissance de l'endothélium vasculaire (VEGF). En plus de son rôle crucial dans le développement des systèmes nerveux et cardiovasculaires, Nrp-1 est impliquée dans des processus physiopathologiques impliquant certains de ses ligands classiques (Sema3 et VEGF) ou récemment caractérisés (TGF-β1 et PDGF) dans les tissus adultes. Dans le système immunitaire, Nrp-1 participe aux interactions entre les lymphocytes T et les cellules dendritiques, transmet les effets immunorégulateurs de Sema3A sur les lymphocytes T, et est impliqué dans le mécanisme suppresseur des lymphocytes T régulateurs (Treg) Foxp3+. Cependant, l'expression de Nrp-1 dans les lymphocytes T non-Treg humains et murins n'a été que peu étudiée. L'objectif de ce projet était de caractériser les populations de lymphocytes T Nrp-1+ non-Treg chez la souris, d'analyser leurs fonctions, d'identifier les mécanismes conduisant à l'expression de Nrp-1 dans ces cellules, et de comprendre le rôle joué par Nrp-1 dans les réponses immunitaires T. Mon travail s'est d'une part intéressé à une population de lymphocytes T non-conventionnels appelés lymphocytes « invariant natural killer T » (iNKT). Les lymphocytes iNKT sont des lymphocytes Tαβ dérivés du thymus aux propriétés immunomodulatrices reposant sur la sécrétion rapide de cytokines TH1 et TH2 après engagement de leur TCR semi-invariant par des complexes CD1d/glycolipide. Un sous-type distinct de cellules iNKT, dont l'origine et l'homéostasie sont encore mal connues, produit la cytokine pro-inflammatoire IL-17. Dans ce travail, j'ai montré que les lymphocytes iNKT émigrés thymiques récents sont identifiés spécifiquement par l'expression de Nrp-1. Les lymphocytes iNKT producteurs d'IL-17 expriment Nrp-1 et dépendent de l'export thymique. D'autre part, Nrp-1 est exprimé par les thymocytes immatures en division et certains lymphocytes Tαβ conventionnels mémoires en prolifération homéostatique rapide. In vitro, l'activation des lymphocytes T par le TCR induit l'expression de Nrp-1 de manière dépendante de la voie de signalisation Ca2+/calcineurine/NFAT. L'expression de Nrp-1 dans les lymphocytes T activés les sensibilise aux effets régulateurs de Sema3A et TGF-β1. En conclusion, ces résultats apportent de nouvelles données concernant l'expression et la fonction de Nrp-1 dans le système immunitaire. Plus généralement, cette étude permet d'envisager des stratégies thérapeutiques ciblant les processus dépendants de Nrp-1 dans les pathologies du système immunitaire et du système nerveux ou les cancers

Expression de la neuropiline-1 dans les lymphocytes T conventionnels et << invariant natural killer T >> (iNKT) mutins

LE KREMLIN-B.- PARIS 11-BU Méd (940432101) / SudocSudocFranceF

Germinal center-dependent and -independent immune responses of tumor-infiltrating B cells in human cancers

Abstract B cells play essential roles in immunity, mainly through the production of high affinity plasma cells (PCs) and memory B (Bmem) cells. The affinity maturation and differentiation of B cells rely on the integration of B-cell receptor (BCR) intrinsic and extrinsic signals provided by antigen binding and the microenvironment, respectively. In recent years, tumor infiltrating B (TIL-B) cells and PCs (TIL-PCs) have been revealed as important players in antitumor responses in human cancers, but their interplay and dynamics remain largely unknown. In lymphoid organs, B-cell responses involve both germinal center (GC)-dependent and GC-independent pathways for Bmem cell and PC production. Affinity maturation of BCR repertoires occurs in GC reactions with specific spatiotemporal dynamics of signal integration by B cells. In general, the reactivation of high-affinity Bmem cells by antigens triggers GC-independent production of large numbers of PC without BCR rediversification. Understanding B-cell dynamics in immune responses requires the integration of multiple tools and readouts such as single-cell phenotyping and RNA-seq, in situ analyses, BCR repertoire analysis, BCR specificity and affinity assays, and functional tests. Here, we review how those tools have recently been applied to study TIL-B cells and TIL-PC in different types of solid tumors. We assessed the published evidence for different models of TIL-B-cell dynamics involving GC-dependent or GC-independent local responses and the resulting production of antigen-specific PCs. Altogether, we highlight the need for more integrative B-cell immunology studies to rationally investigate TIL-B cells as a leverage for antitumor therapies

Heterogeneity of germinal center B cells: New insights from single‐cell studies

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The "French Germinal Center Club" of the French Society for Immunology: a dynamic collaboration between researchers passionate about the germinal center reaction

International audienceThe antibody response and B cell memory development are major effector arms of the immune system. They both rely on the selection of B cells in specific anatomical structures called germinal centers (GC). GCs are not only sites for clonal B cell expansion but also the places where the antibody repertoire diversifies following somatic hypermutations and class switch recombination. CD4+ T cells that are present in GCs guide the stringent cell selection of high-affinity B cell variants. They can be divided in two functional cell subsets: T follicular helper (Tfh) and T follicular regulatory (Tfr) cells. Furthermore, follicular B and T cell subsets are in close contact with specialized stromal cells allowing cell migration, adhesion, and participating in B cell selection mechanisms. Importantly, on top of their essential role as orchestrators of protective immune responses against infections, GCs have also been involved in diverse pathological conditions including autoimmunity, allergy, and cancer. The great complexity of these structures means that GC aficionados encompass researchers working on a very large palette of topics including in depth analysis of the immune cell types cited above, characterization of cell interactions between GC immune and/or mesenchymal cell subsets, as well as deciphering disease physiopathology. The great versatility of these research foci means that the GC field is extremely dynamic and multidisciplinary. However, because there are many scientific topics addressed when studying GC and despite a consequent number of teams interested in this field, events centered only on GCs allowing researcher interactions are quite rare

Des lymphocytes « très spéciaux » ciblent des antigènes du soi dans l’hépatite auto-immune

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ShIVA: a user-friendly and interactive interface giving biologists control over their single-cell RNA-seq data

Abstract Single-cell technologies have revolutionised biological research and applications. As they continue to evolve with multi-omics and spatial resolution, analysing single-cell datasets is becoming increasingly complex. For biologists lacking expert data analysis resources, the problem is even more crucial, even for the simplest single-cell transcriptomics datasets. We propose ShIVA, an interface for the analysis of single-cell RNA-seq and CITE-seq data specifically dedicated to biologists. Intuitive, iterative and documented by video tutorials, ShIVA allows biologists to follow a robust and reproducible analysis process, mostly based on the Seurat v4 R package, to fully explore and quantify their dataset, to produce useful figures and tables and to export their work to allow more complex analyses performed by experts

FB5P-seq: FACS-Based 5-Prime End Single-Cell RNA-seq for Integrative Analysis of Transcriptome and Antigen Receptor Repertoire in B and T Cells

International audienceSingle-cell RNA sequencing (scRNA-seq) allows the identification, characterization, and quantification of cell types in a tissue. When focused on B and T cells of the adaptive immune system, scRNA-seq carries the potential to track the clonal lineage of each analyzed cell through the unique rearranged sequence of its antigen receptor (BCR or TCR, respectively) and link it to the functional state inferred from transcriptome analysis. Here we introduce FB5P-seq, a FACS-based 5′-end scRNA-seq method for cost-effective, integrative analysis of transcriptome and paired BCR or TCR repertoire in phenotypically defined B and T cell subsets. We describe in detail the experimental workflow and provide a robust bioinformatics pipeline for computing gene count matricesand reconstructing repertoire sequences from FB5P-seq data. We further present two applications of FB5P-seq for the analysis of human tonsil B cell subsets and peripheral blood antigen-specific CD4T cells. We believe th at our novel integrative scRNA-seq method will be a valuable option to study rare adap tive immune cell subsets in immunology research