CpG-ODN-induced sustained expression of BTLA mediating selective inhibition of human B cells

BTLA (B- and T-lymphocyte attenuator) is a prominent co-receptor that is structurally and functionally related to CTLA-4 and PD-1. In T cells, BTLA inhibits TCR-mediated activation. In B cells, roles and functions of BTLA are still poorly understood and have never been studied in the context of B cells activated by CpG via TLR9. In this study, we evaluated the expression of BTLA depending on activation and differentiation of human B cell subsets in peripheral blood and lymph nodes. Stimulation with CpG upregulated BTLA, but not its ligand: herpes virus entry mediator (HVEM), on B cells in vitro and sustained its expression in vivo in melanoma patients after vaccination. Upon ligation with HVEM, BTLA inhibited CpG-mediated B cell functions (proliferation, cytokine production, and upregulation of co-stimulatory molecules), which was reversed by blocking BTLA/HVEM interactions. Interestingly, chemokine secretion (IL-8 and MIP1β) was not affected by BTLA/HVEM ligation, suggesting that BTLA-mediated inhibition is selective for some but not all B cell functions. We conclude that BTLA is an important immune checkpoint for B cells, as similarly known for T cell

PD-1 et BTLA au coeur des lymphocytes B : du physiologique aux lymphomes

La réponse immunitaires est régulée par des molécules de co-signalisation, qui, en apportant des signaux inhibiteurs ou activateurs, modulent les fonctions lymphocytaires. Nous avons focalisé notre étude sur deux co-effecteurs et membres de la famille CD28/B7 : PD-1 (Programmed Death 1) et BTLA (B and T Lymphocyte Attenuator), tous deux décrits, à l’image de CTLA-4, comme inhibitrices de l’activation lymphocytaire T. Au cours de ma thèse, nous avons pu évaluer l’expression et le rôle de PD-1 et BTLA sur les lymphocytes B normaux et pathologiques. Dans une première partie, nos travaux ont montré que ces molécules sont exprimées à la surface des sous populations B du sang périphérique et des tissus et qu’elles sont également finement régulées au cours de l’activation B. Par la suite nous avons démontré pour la première fois que BTLA et PD-1, à l’image des cellules T, sont recrutées, après activation, au niveau du récepteur de la cellule B et qu’elles exercent un rôle inhibiteur sur l’activation de ces mêmes cellules. Dans une seconde partie, grâce au développement d’un outil en cytométrie multicouleurs, nous avons analysé, dans une cohorte de 72 lymphomes B, l’infiltrat immunitaire ainsi que l’expression de PD-1, BTLA et leurs ligands. Ce travail, par son analyse de la physiologie B d’une part et de pathologies tumorales B d’autre part, donne un nouvel éclairage sur les rôles complexes des co-récepteurs BTLA et PD-1.The immune response is regulated by co-signaling molecules, which, by providing signals inhibitors or activators, modulate lymphocyte functions. We focused our study on two co-effectors and CD28/B7 family members: PD-1 (Programmed Death 1) and BTLA (B and T Lymphocyte Attenuator), both described, like CTLA-4, as inhibitors of T lymphocyte activation. This work allowed us to evaluate the expression and the role of BTLA and PD-1 on normal and tumoral B lymphocytes. In the first part, our work has shown that these molecules are expressed on B cell subsets of peripheral blood and tissues and are also finely regulated during the B cell activation. Subsequently, we have demonstrated for the first time that BTLA and PD-1, like T cells, are recruited after activation at the B cell receptor, and they exert an inhibitory role on the activation of these cells. In the second part, through the development of a multicolor cytometry tool, we analyzed the immune infiltrate and the expression of PD-1, BTLA and their ligands in a cohort of 72 B-cell lymphomas. Taken together, these results, by his analysis of the physiology of B cell from B cell malignancies, give a new insight into the complex roles of BTLA and PD-1 co-receptors

Identification of druggable inhibitory immune checkpoints on Natural Killer cells in COVID-19

International audienceInfection with SARS-COV-2 is the cause of COVID-19 and has generated an unprecedented health crisis worldwide. While most of the patients experience mild symptoms, around 20% develop severe disease, characterized by pneumonia and in the worst cases by acute respiratory distress syndrome (ARDS).1 The analysis and understanding of the immune responses arising in the course of SARS-COV-2 infection may help to propose therapeutic solutions. Due to the crucial role of Natural Killer (NK) cells in antiviral immune responses,2 we analyzed NK cells in blood from a cohort of 82 individuals: 10 healthy controls (HC), 10 paucisymptomatic COVID-19 patients (pauci), 34 patients with pneumonia (pneumo) and 28 patients with ARDS due to SARS-CoV-2 infection. The absolute numbers of peripheral blood NK cells, B, CD4+, and CD8+ T lymphocytes were lower in the pneumonia and ARDS groups than in healthy controls, consistent with previously published results3 (Fig. 1a). We investigated the NK cell subsets further and found that among CD45+CD3−CD56+ total NK cells the proportion of mature NK cells, a subset defined on the basis of its expression of the CD16 and CD57 cell surface receptors, was markedly lower in patients with ARDS (Fig. 1b). Given their role in viral infection, the loss of mature NK cells may contribute to the pulmonary complications occurring in the most severe cases of COVID-19. We then focused our analysis on molecular pathways likely to improve NK cell antiviral activity to promote SARS-CoV-2 clearance, and analyzed the expression of several immune checkpoints. Given the availability of therapeutic monoclonal antibodies blocking the immunosuppressive functions of PD-1,4 NKG2A,5 and CD396 initially developed for cancer therapies, we analyzed the expression of these molecules on NK cells in our cohort. PD-1 and NKG2A are cell surface receptors, and their engagement with their ligands, PD-L1 and HLA-E, respectively, inhibits the function of T and NK cells. CD39 is an ectoenzyme that cleaves extracellular ATP and ADP, which can be released from dead cells upon viral infection, leading to the generation of adenosine, which has strong immunosuppressive effects on T and NK cells

Identification of druggable inhibitory immune checkpoints on Natural Killer cells in COVID-19

International audienceInfection with SARS-COV-2 is the cause of COVID-19 and has generated an unprecedented health crisis worldwide. While most of the patients experience mild symptoms, around 20% develop severe disease, characterized by pneumonia and in the worst cases by acute respiratory distress syndrome (ARDS).1 The analysis and understanding of the immune responses arising in the course of SARS-COV-2 infection may help to propose therapeutic solutions. Due to the crucial role of Natural Killer (NK) cells in antiviral immune responses,2 we analyzed NK cells in blood from a cohort of 82 individuals: 10 healthy controls (HC), 10 paucisymptomatic COVID-19 patients (pauci), 34 patients with pneumonia (pneumo) and 28 patients with ARDS due to SARS-CoV-2 infection. The absolute numbers of peripheral blood NK cells, B, CD4+, and CD8+ T lymphocytes were lower in the pneumonia and ARDS groups than in healthy controls, consistent with previously published results3 (Fig. 1a). We investigated the NK cell subsets further and found that among CD45+CD3−CD56+ total NK cells the proportion of mature NK cells, a subset defined on the basis of its expression of the CD16 and CD57 cell surface receptors, was markedly lower in patients with ARDS (Fig. 1b). Given their role in viral infection, the loss of mature NK cells may contribute to the pulmonary complications occurring in the most severe cases of COVID-19. We then focused our analysis on molecular pathways likely to improve NK cell antiviral activity to promote SARS-CoV-2 clearance, and analyzed the expression of several immune checkpoints. Given the availability of therapeutic monoclonal antibodies blocking the immunosuppressive functions of PD-1,4 NKG2A,5 and CD396 initially developed for cancer therapies, we analyzed the expression of these molecules on NK cells in our cohort. PD-1 and NKG2A are cell surface receptors, and their engagement with their ligands, PD-L1 and HLA-E, respectively, inhibits the function of T and NK cells. CD39 is an ectoenzyme that cleaves extracellular ATP and ADP, which can be released from dead cells upon viral infection, leading to the generation of adenosine, which has strong immunosuppressive effects on T and NK cells

PD-1 is a novel regulator of human B-cell activation

International audienceThe outcome of the adaptive immune response is determined by the integration of both positive and negative signals, respectively, induced upon the triggering of co-signaling receptors. One of them, programmed cell death 1 (PDCD1/PD-1) has largely been shown to be involved in the negative regulation of T-cell activation. However, PD-1 is also expressed on human B cells, and its role(s) in the process of human B-cell activation remains uncertain thus far. In this study, we describe the expression of PD-1 on the major human B-cells subsets isolated from peripheral blood and lymph nodes. We showed that PD-1 was expressed on naive B cells, was differentially expressed on peripheral IgM memory as compared with memory B cells and was lost on germinal center B cells. Expression of PD-1 ligands (PD-Ls) was induced by TLR9 activation. Finally, we showed that PD-1 was recruited to the B-cell receptor upon triggering. We determined that during TLR9 activation, blockade of PD-1/PD-Ls pathways indeed increased B-cell activation, proliferation and the production of inflammatory cytokines. Altogether, our results show, that, as reported in T cells, PD-1/PD-Ls complexes acted as inhibitors of the B-cell activation cascade and highlight the importance of devising future therapies able to modulate lymphocyte activation through the targeting of the PD-1/PD-Ls pathways

High expression of indoleamine 2,3-dioxygenase in the tumour is associated with medullary features and favourable outcome in basal-like breast carcinoma

Medullary breast cancer (MBC) is a basal-like breast carcinoma (BLBC) with a favourable outcome, whereas nonmedullary BLBC has a poor prognosis. Tumour infiltrating lymphocytes (TILs) are present in both MBC and BLBC. We hypothesized that the immunosuppressive enzyme indoleamine 2,3-dioxygenase (IDO) could modulate the TILs effects among these tumours and explain their different outcomes. The amount of TILs and IDO expression were analysed using immunohistochemistry (IHC) in 155 BC cases including MBC (n = 17), atypical MBC (n = 13) and non-MBC (n = 125). Messenger RNA expression of the INDO gene, which encodes IDO, was measured in 262 cases from our institution. INDO mRNA expression and histoclinical data of 1,487 BC cases were collected from public databases. IDO immunostaining was present in both neoplastic and stromal cells in 100% of MBC and was associated with histological medullary features among non-MBC cases. There was a significant correlation between IDO positivity and TIL amounts. In our series including mostly grade-3 BC, IDO immunostaining was the most significant marker (p = 0.02) associated with better survival in multivariate analysis. Among our 262 analysed BC cases, INDO mRNA showed significant overexpression in BLBC as compared to luminal A tumours, and in MBC as compared to basal-like non-MBC. In the pooled series of 1,749 BC cases, INDO mRNA was overexpressed in BLBC and was the most significant predictor of better survival in this subtype using multivariate analysis (p = 0.0024). In conclusion, high IDO expression is associated with morphological medullary features and has an independent favourable prognostic value in BLBC

Peripheral Blood NK Cells from Breast Cancer Patients Are Tumor-Induced Composite Subsets

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Follicular Lymphoma B Cells Generate Functional Regulatory T Cells Via ICOS/ICOSL Pathway and Are Inhibited By Intratumoral Tregs

WOS:000368021803321International audience55th Annual Meeting and Exposition of the American-Society-of-Hematology - New Orleans, LA 201