Impact of BRAFV600E mutation on aggressiveness and outcomes in adult clonal histiocytosis

Histiocytoses encompass a wide spectrum of diseases, all characterized by tissue infiltration by CD68+ histiocytes. Most adult histiocytoses are considered clonal diseases because they highlight recurrent somatic mutations in the MAP-kinase pathway gene, primarily BRAF. The presence of BRAF mutation is associated with widespread disease in children with Langerhans cell histiocytosis (LCH) or cardiovascular/neurological involvement in Erdheim–Chester disease (ECD). Nevertheless, few data are available on adult clonal histiocytosis. This is why we have conducted a retrospective study of all patients with clonal histiocytosis in our institution and present the data according to the presence of BRAF mutation. Among 27 adult patients (10 ECD, 10 LCH, 5 Rosai–Dorfman disease (RDD), and 3 mixed ECD/LCH), 11 (39%) have BRAF mutation with gain of function (n = 9) and deletion (n = 2). Those patients had frequent multicentric disease with risk organ involvement, especially the brain and cardiovascular system. They had frequent associated myeloid neoplasms (mostly chronic myelomonocytic leukemia) and received more frequently targeted therapy as the front-line therapy. Nevertheless, its presence did not affect the overall survival or relapse-free survival probably due to the emergence of efficient therapies. To conclude, rapid and accurate molecular establishment in adult clonal histiocytoses is crucial because BRAFV600E mutation correlates with multicentric disease with organ involvement and incomplete metabolic response

Cytotoxic dendritic cells generated from cancer patients.

International audienceKnown for years as professional APCs, dendritic cells (DCs) are also endowed with tumoricidal activity. This dual role of DC as killers and messengers may have important implications for tumor immunotherapy. However, the tumoricidal activity of DCs has mainly been investigated in animal models. Cancer cells inhibit antitumor immune responses using numerous mechanisms, including the induction of immunosuppressive/ tolerogenic DCs that have lost their ability to present Ags in an immunogenic manner. In this study, we evaluated the possibility of generating tumor killer DCs from patients with advanced-stage cancers. We demonstrate that human monocyte-derived DCs are endowed with significant cytotoxic activity against tumor cells following activation with LPS. The mechanism of DC-mediated tumor cell killing primarily involves peroxynitrites. This observed cytotoxic activity is restricted to immature DCs. Additionally, after killing, these cytotoxic DCs are able to activate tumor Ag-specific T cells. These observations may open important new perspectives for the use of autologous cytotoxic DCs in cancer immunotherapy strategies

Splenic TFH expansion participates in B-cell differentiation and antiplatelet-antibody production during immune thrombocytopenia

Antiplatelet-antibody-producing B cells play a key role immune thrombocytopenia (ITP) pathogenesis; however, little is known about T-cell dysregulations that support B-cell differentiation. During the past decade, T follicular helper cells (TFHs) have been characterized as the main T-cell subset within secondary lymphoid organs that promotes B-cell differentiation leading to antibody class-switch recombination and secretion. Herein, we characterized TFHs within the spleen of 8 controls and 13 ITP patients. We show that human splenic TFHs are the main producers of interleukin (IL)-21, express CD40 ligand(CD154), and are located within the germinal center of secondary follicles. Compared with controls, splenic TFH frequency is higher in ITP patients and correlates with germinal center and plasma cell percentages that are also increased. In vitro, IL-21 stimulation combined with an anti-CD40 agonist antibody led to the differentiation of splenic B cells into plasma cells and to the secretion of antiplatelet antibodies in ITP patients. Overall, these results point out the involvement of TFH in ITP pathophysiology and the potential interest of IL-21 and CD40 as therapeutic targets in ITP

Study of immune thrombocytopenia pathogenesis

La thrombopénie immunologique ou purpura thrombopénique immunologique (PTI) est une maladie auto-immune rare responsable d’une destruction périphérique immunologique des plaquettes associée à une production médullaire inadaptée. Dans la première partie de ce travail, nous exposons les connaissances actuelles de sa physiopathologie ainsi que certaines données concernant la réponse immunitaire T, le rôle des lymphocytes T régulateurs (Treg), l’implication de la rate dans la réponse immunitaire ainsi que les modes d’action d’une thérapeutique anti-lymphocytaire B, le rituximab. Dans une seconde partie, nous rapportons les résultats obtenus chez 40 patients atteints de PTI. Nous avons montré que le taux des Treg circulants CD4+CD25HighFoxp3+ est similaire chez les patients et les témoins, avec une élévation de leur taux chez les sujets répondeurs aux traitements. A l’inverse, il existe un déficit quantitatif en Treg au sein de la rate des patients. L’analyse des sous-populations lymphocytaires B spléniques a montré une augmentation du taux de lymphocytes B de la zone marginale chez les patients. Concernant les mécanismes d’action du rituximab, nous avons montré qu’une déplétion lymphocytaire B sanguine et splénique n’est pas suffisante pour obtenir une rémission, et que les plasmocytes ne sont pas sensibles à cette thérapeutique. Par ailleurs, nous proposons un mécanisme d’échappement à ce traitement. En effet, nous avons montré que les patients résistants au RTX présentent une élévation du ratio Th1/Treg spléniques. Chez ces sujets non répondeurs, nous avons également observé une élévation du ratio lymphocytes T CD8+/CD4+, au sein de la rate, suggérant une participation des lymphocytes T cytotoxiques dans la physiopathologie du PTI. Ces résultats ouvrent donc de nouvelles perspectives dans la compréhension de la physiopathologie du PTI, notamment la possible implication des lymphocytes B de la zone marginale et le défaut de contrôle de la réponse immunitaire splénique par les Treg. Concernant le rituximab, son action sur la réponse immunitaire ne semble pas se limiter à une déplétion lymphocytaire B qui n’est pas suffisante pour obtenir une rémission. Un mécanisme d’échappement ou de résistance à cette thérapeutique passe par une orientation Th1 et une probable implication des lymphocytes T CD8+.Immune thrombocytopenia (ITP) is an autoimmune disease responsible for a peripheral immune destruction of platelets associated with an inappropriate bone marrow production. In this work, we first review the mechanisms involved in the pathogenesis of ITP. We also focus on the T cell immune response, highlighting the key role of regulatory T cells (Treg) in peripheral tolerance. The implication of the spleen in the immune response and the effects of rituximab, a B cell depleting therapy, are discussed. Then, our results obtained from 40 ITP patients are reported. Despite the fact that CD4+CD25HighFoxp3+ circulating Treg levels are similar between patients and controls, a significant increase is observed in responder patients. In the spleen, the rate of Treg is lower in ITP patients. Analyses of the spleens also reveal an increase in the level of marginal zone B cells in ITP. Rituximab is responsible for a complete depletion of both circulating and splenic B cells, which is not sufficient to achieve a response. Moreover, plasma cells are still observed after treatment. An increase in the Th1/Treg ratio in the spleen of non responder patients after rituximab infusion could trigger an escape to this therapy. The involvement of CD8+ T cells in the pathogenesis of ITP is highlighted by the increase in the CD8+/CD4+ ratio in the spleen after rituximab. New fields in the understanding of the pathogenesis of ITP are opened with these results, particularly by showing a quantitative deficiency in splenic Treg and the possible involvement of marginal zone B cells. Regarding rituximab effect on the immune response, we demonstrate on the one hand that complete circulating and splenic B cell depletion is not sufficient to achieve remission, and on the other hand that Th1 response and increase in CD8+ T cells level may represent an escape to this treatment

Etude physiopathologique de la réponse immunitaire au cours de la thrombopénie immunologique (purpura thrombopénique immunologique)

Immune thrombocytopenia (ITP) is an autoimmune disease responsible for a peripheral immune destruction of platelets associated with an inappropriate bone marrow production. In this work, we first review the mechanisms involved in the pathogenesis of ITP. We also focus on the T cell immune response, highlighting the key role of regulatory T cells (Treg) in peripheral tolerance. The implication of the spleen in the immune response and the effects of rituximab, a B cell depleting therapy, are discussed. Then, our results obtained from 40 ITP patients are reported. Despite the fact that CD4+CD25HighFoxp3+ circulating Treg levels are similar between patients and controls, a significant increase is observed in responder patients. In the spleen, the rate of Treg is lower in ITP patients. Analyses of the spleens also reveal an increase in the level of marginal zone B cells in ITP. Rituximab is responsible for a complete depletion of both circulating and splenic B cells, which is not sufficient to achieve a response. Moreover, plasma cells are still observed after treatment. An increase in the Th1/Treg ratio in the spleen of non responder patients after rituximab infusion could trigger an escape to this therapy. The involvement of CD8+ T cells in the pathogenesis of ITP is highlighted by the increase in the CD8+/CD4+ ratio in the spleen after rituximab. New fields in the understanding of the pathogenesis of ITP are opened with these results, particularly by showing a quantitative deficiency in splenic Treg and the possible involvement of marginal zone B cells. Regarding rituximab effect on the immune response, we demonstrate on the one hand that complete circulating and splenic B cell depletion is not sufficient to achieve remission, and on the other hand that Th1 response and increase in CD8+ T cells level may represent an escape to this treatment.La thrombopénie immunologique ou purpura thrombopénique immunologique (PTI) est une maladie auto-immune rare responsable d’une destruction périphérique immunologique des plaquettes associée à une production médullaire inadaptée. Dans la première partie de ce travail, nous exposons les connaissances actuelles de sa physiopathologie ainsi que certaines données concernant la réponse immunitaire T, le rôle des lymphocytes T régulateurs (Treg), l’implication de la rate dans la réponse immunitaire ainsi que les modes d’action d’une thérapeutique anti-lymphocytaire B, le rituximab. Dans une seconde partie, nous rapportons les résultats obtenus chez 40 patients atteints de PTI. Nous avons montré que le taux des Treg circulants CD4+CD25HighFoxp3+ est similaire chez les patients et les témoins, avec une élévation de leur taux chez les sujets répondeurs aux traitements. A l’inverse, il existe un déficit quantitatif en Treg au sein de la rate des patients. L’analyse des sous-populations lymphocytaires B spléniques a montré une augmentation du taux de lymphocytes B de la zone marginale chez les patients. Concernant les mécanismes d’action du rituximab, nous avons montré qu’une déplétion lymphocytaire B sanguine et splénique n’est pas suffisante pour obtenir une rémission, et que les plasmocytes ne sont pas sensibles à cette thérapeutique. Par ailleurs, nous proposons un mécanisme d’échappement à ce traitement. En effet, nous avons montré que les patients résistants au RTX présentent une élévation du ratio Th1/Treg spléniques. Chez ces sujets non répondeurs, nous avons également observé une élévation du ratio lymphocytes T CD8+/CD4+, au sein de la rate, suggérant une participation des lymphocytes T cytotoxiques dans la physiopathologie du PTI. Ces résultats ouvrent donc de nouvelles perspectives dans la compréhension de la physiopathologie du PTI, notamment la possible implication des lymphocytes B de la zone marginale et le défaut de contrôle de la réponse immunitaire splénique par les Treg. Concernant le rituximab, son action sur la réponse immunitaire ne semble pas se limiter à une déplétion lymphocytaire B qui n’est pas suffisante pour obtenir une rémission. Un mécanisme d’échappement ou de résistance à cette thérapeutique passe par une orientation Th1 et une probable implication des lymphocytes T CD8+

Etude physiopathologique de la réponse immunitaire au cours de la thrombopénie immunologique (purpura thrombopénique immunologique)

Immune thrombocytopenia (ITP) is an autoimmune disease responsible for a peripheral immune destruction of platelets associated with an inappropriate bone marrow production. In this work, we first review the mechanisms involved in the pathogenesis of ITP. We also focus on the T cell immune response, highlighting the key role of regulatory T cells (Treg) in peripheral tolerance. The implication of the spleen in the immune response and the effects of rituximab, a B cell depleting therapy, are discussed. Then, our results obtained from 40 ITP patients are reported. Despite the fact that CD4+CD25HighFoxp3+ circulating Treg levels are similar between patients and controls, a significant increase is observed in responder patients. In the spleen, the rate of Treg is lower in ITP patients. Analyses of the spleens also reveal an increase in the level of marginal zone B cells in ITP. Rituximab is responsible for a complete depletion of both circulating and splenic B cells, which is not sufficient to achieve a response. Moreover, plasma cells are still observed after treatment. An increase in the Th1/Treg ratio in the spleen of non responder patients after rituximab infusion could trigger an escape to this therapy. The involvement of CD8+ T cells in the pathogenesis of ITP is highlighted by the increase in the CD8+/CD4+ ratio in the spleen after rituximab. New fields in the understanding of the pathogenesis of ITP are opened with these results, particularly by showing a quantitative deficiency in splenic Treg and the possible involvement of marginal zone B cells. Regarding rituximab effect on the immune response, we demonstrate on the one hand that complete circulating and splenic B cell depletion is not sufficient to achieve remission, and on the other hand that Th1 response and increase in CD8+ T cells level may represent an escape to this treatment.La thrombopénie immunologique ou purpura thrombopénique immunologique (PTI) est une maladie auto-immune rare responsable d’une destruction périphérique immunologique des plaquettes associée à une production médullaire inadaptée. Dans la première partie de ce travail, nous exposons les connaissances actuelles de sa physiopathologie ainsi que certaines données concernant la réponse immunitaire T, le rôle des lymphocytes T régulateurs (Treg), l’implication de la rate dans la réponse immunitaire ainsi que les modes d’action d’une thérapeutique anti-lymphocytaire B, le rituximab. Dans une seconde partie, nous rapportons les résultats obtenus chez 40 patients atteints de PTI. Nous avons montré que le taux des Treg circulants CD4+CD25HighFoxp3+ est similaire chez les patients et les témoins, avec une élévation de leur taux chez les sujets répondeurs aux traitements. A l’inverse, il existe un déficit quantitatif en Treg au sein de la rate des patients. L’analyse des sous-populations lymphocytaires B spléniques a montré une augmentation du taux de lymphocytes B de la zone marginale chez les patients. Concernant les mécanismes d’action du rituximab, nous avons montré qu’une déplétion lymphocytaire B sanguine et splénique n’est pas suffisante pour obtenir une rémission, et que les plasmocytes ne sont pas sensibles à cette thérapeutique. Par ailleurs, nous proposons un mécanisme d’échappement à ce traitement. En effet, nous avons montré que les patients résistants au RTX présentent une élévation du ratio Th1/Treg spléniques. Chez ces sujets non répondeurs, nous avons également observé une élévation du ratio lymphocytes T CD8+/CD4+, au sein de la rate, suggérant une participation des lymphocytes T cytotoxiques dans la physiopathologie du PTI. Ces résultats ouvrent donc de nouvelles perspectives dans la compréhension de la physiopathologie du PTI, notamment la possible implication des lymphocytes B de la zone marginale et le défaut de contrôle de la réponse immunitaire splénique par les Treg. Concernant le rituximab, son action sur la réponse immunitaire ne semble pas se limiter à une déplétion lymphocytaire B qui n’est pas suffisante pour obtenir une rémission. Un mécanisme d’échappement ou de résistance à cette thérapeutique passe par une orientation Th1 et une probable implication des lymphocytes T CD8+

Emerging Therapies in Immune Thrombocytopenia

Immune thrombocytopenia (ITP) is a rare autoimmune disorder caused by peripheral platelet destruction and inappropriate bone marrow production. The management of ITP is based on the utilization of steroids, intravenous immunoglobulins, rituximab, thrombopoietin receptor agonists (TPO-RAs), immunosuppressants and splenectomy. Recent advances in the understanding of its pathogenesis have opened new fields of therapeutic interventions. The phagocytosis of platelets by splenic macrophages could be inhibited by spleen tyrosine kinase (Syk) or Bruton tyrosine kinase (BTK) inhibitors. The clearance of antiplatelet antibodies could be accelerated by blocking the neonatal Fc receptor (FcRn), while new strategies targeting B cells and/or plasma cells could improve the reduction of pathogenic autoantibodies. The inhibition of the classical complement pathway that participates in platelet destruction also represents a new target. Platelet desialylation has emerged as a new mechanism of platelet destruction in ITP, and the inhibition of neuraminidase could dampen this phenomenon. T cells that support the autoimmune B cell response also represent an interesting target. Beyond the inhibition of the autoimmune response, new TPO-RAs that stimulate platelet production have been developed. The upcoming challenges will be the determination of predictive factors of response to treatments at a patient scale to optimize their management

Purpura thrombopénique auto-immun (étude descriptive et rôle des lymphocytes T régulateurs)

DIJON-BU Médecine Pharmacie (212312103) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF

Immune Thrombocytopenia: Recent Advances in Pathogenesis and Treatments

Immune thrombocytopenia (ITP) is a rare autoimmune disease due to both a peripheral destruction of platelets and an inappropriate bone marrow production. Although the primary triggering factors of ITP remain unknown, a loss of immune tolerance—mostly represented by a regulatory T-cell defect—allows T follicular helper cells to stimulate autoreactive splenic B cells that differentiate into antiplatelet antibody-producing plasma cells. Glycoprotein IIb/IIIa is the main target of antiplatelet antibodies leading to platelet phagocytosis by splenic macrophages, through interactions with Fc gamma receptors (FcγRs) and complement receptors. This allows macrophages to activate autoreactive T cells by their antigen-presenting functions. Moreover, the activation of the classical complement pathway participates to platelet opsonization and also to their destruction by complement-dependent cytotoxicity. Platelet destruction is also mediated by a FcγR-independent pathway, involving platelet desialylation that favors their binding to the Ashwell-Morell receptor and their clearance in the liver. Cytotoxic T cells also contribute to ITP pathogenesis by mediating cytotoxicity against megakaryocytes and peripheral platelets. The deficient megakaryopoiesis resulting from both the humoral and the cytotoxic immune responses is sustained by inappropriate levels of thrombopoietin, the major growth factor of megakaryocytes. The better understanding of ITP pathogenesis has provided important therapeutic advances. B cell-targeting therapies and thrombopoietin-receptor agonists (TPO-RAs) have been used for years. New emerging therapeutic strategies that inhibit FcγR signaling, the neonatal Fc receptor or the classical complement pathway, will deeply modify the management of ITP in the near future