Search

Introduction: CD39 plays an important role in the immunoregulation and inhibition of effector cells. It is expressed on immune cells, including Tregs, and on extracellular vesicles (EVs) budding from the plasma membrane. Platelet transfusion may induce alloimmunization against HLA-I antigens, leading to refractoriness to platelet transfusion with severe consequences for patients. Tregs may play a key role in determining whether alloimmunization occurs in patients with hematologic disorders. We hypothesized that CD39+ EVs might play an immunoregulatory role, particularly in the context of platelet transfusions in patients with hematologic disorders. Such alloimmunization leads to the production of alloantibodies and is sensitive to the regulatory action of CD39. Methods: We characterized CD39+ EVs in platelet concentrates by flow cytometry. The absolute numbers and cellular origins of CD39+ EVs were evaluated. We also performed functional tests to evaluate interactions with immune cells and their functions. Results: We found that CD39+ EVs from platelet concentrates had an inhibitory phenotype that could be transferred to the immune cells with which they interacted: CD4+ and CD8+ T lymphocytes (TLs), dendritic cells, monocytes, and B lymphocytes (BLs). Moreover, the concentration of CD39+ EVs in platelet concentrates varied and was very high in 10% of concentrates. The number of these EVs present was determinant for EV-cell interactions. Finally, functional interactions were observed with BLs, CD4+ TLs and CD39+ EVs for immunoglobulin production and lymphoproliferation, with potential implications for the immunological management of patients. [ABSTRACT FROM AUTHOR]

Introduction: People living with HIV (PLWH) now benefit from combined antiviral treatments that durably control viral replication. These antiretroviral treatments decrease mortality and improve quality of life in PLWH, but do not completely control the excessive non-specific activation of the immune system in PLWH. This chronic immune activation is a key element of HIV immunopathology that contributes to the pathophysiology of inflammatory comorbid conditions, such as cardiovascular disorders, cancer and autoimmune diseases. Circulating nonexosomal extracellular vesicles, also known as microparticles (MPs) are detected in these diseases and have been linked to immune activation. The objective of this study was to characterize the MPs present in PLWH and to assess their association with chronic immune activation. Methods: We performed flow cytometry for the complete phenotypic characterization of MPs from fresh plasma from PLWH and from people without HIV as the control group. The absolute number, size and cellular origin of MPs were evaluated. The immunoregulatory profile was determined by cell origin, for MPs derived from platelets (PMPs), monocytes (MMPs) and T lymphocytes (LMPs). Results: PLWH had significantly more circulating MPs than controls, for MPs of all sizes originating from T lymphocytes, red blood cells, neutrophils, dendritic cells, B lymphocytes and endothelial cells. PMPs and MMPs were not more numerous in PLWH, but the immunoregulatory phenotypes of these MPs differed between PLWH and controls. These differences in immunoregulatory molecule expression. [ABSTRACT FROM AUTHOR]

Introduction: Acute myeloid leukemia (AML) is one of the commonest hematologic disorders. Due to the high frequency of disease- or treatment-related thrombocytopenia, AML requires treatment with multiple platelet transfusions, which can trigger a humoral response directed against platelets. Some, but not all, AML patients develop an anti-HLA immune response after multiple transfusions. We therefore hypothesized that different immune activation profiles might be associated with anti-HLA alloimmunization status. Methods: We tested this hypothesis, by analyzing CD4+ T lymphocyte (TL) subsets and their immune control molecules in flow cytometry and single-cell multi-omics. Results: A comparison of immunological status between anti-HLA alloimmunized and non-alloimmunized AML patients identified differences in the phenotype and function of CD4+ TLs. CD4+ TLs from alloimmunized patients displayed features of immune activation, with higher levels of CD40 and OX40 than the cells of healthy donors. However, the most notable differences were observed in non-alloimmunized patients. These patients had lower levels of CD40 and OX40 than alloimmunized patients and higher levels of PD1. Moreover, the Treg compartment of non-alloimmunized patients was larger and more functional than that in alloimmunized patients. These results were supported by a multi-omics analysis of immune response molecules in conventional CD4+ TLs, Tfh circulating cells, and Tregs. Discussion: Our results thus reveal divergent CD4+ TL characteristics correlated with anti-HLA alloimmunization status in transfused AML patients. These differences, characterizing CD4+ TLs independently of any specific antigen, should be taken into account when considering the immune responses of patients to infections, vaccinations, or transplantations. [ABSTRACT FROM AUTHOR]

Extracellular vesicles (EVs), which are generated by cell membrane budding in diverse cells, are present in variable numbers in the blood. An immunoregulatory role has been demonstrated principally for heterologous EVs, but the function of the EVs present naturally in blood remains unknown. We hypothesize that these autologous EVs might also modulate the phenotype and function of immune system cells, especially CD4+ T lymphocytes (TLs), as previously described for heterologous EVs. Several membranes and soluble immunoregulatory molecules were studied after the treatment of CD4+ TLs with autologous EVs. No direct activation was detected with autologous EVs, contrasting with the findings for heterologous EVs. However, following treatment with autologous EVs, a soluble form of CD27 (sCD27) was detected. sCD27 is strongly associated with lymphoproliferation. Autologous EVs have been shown to increase TL proliferation only after T-cell receptor (TcR) engagement due to polyclonal or specific-antigen stimulation. Our results therefore suggest that the EVs present in the blood have an immunomodulatory role different from that of heterologous EVs. These findings should be taken into account in future studies, particularly those focusing on infectious diseases, autotransfusion or doping practices. [ABSTRACT FROM AUTHOR]

Keywords: CCR7 receptor; CXCR4 receptor; whole blood; chemoattraction; red blood cell alloimmunization; Treg EN CCR7 receptor CXCR4 receptor whole blood chemoattraction red blood cell alloimmunization Treg 477 481 5 07/19/21 20210715 NES 210715 Understanding the mechanisms of the human immune response against red blood cell (RBC) antigens is a major issue for transfused patients.1,2 CD4 SP + sp T lymphocytes (TLs) play a key role in these reactions.3,4 Previously described by our group and others, several information are available about TL phenotypes and functions [regulatory T cells (Treg), T-helper cells type 17 (Th17) and follicular helper T cells (Tfh)],5-10 but little is known about the encounter of T cells with B cells leading to B-cell differentiation and antibody production in this context. Interleukin-6 receptor-alpha signaling drives anti-RBC alloantibody production and T-follicular helper cell differentiation in a murine model of red blood cell alloimmunization. (A) RBC alloantibody numbers in alloimmunized sickle cell disease (SCD) patients, and (B) RBC alloantibody specificities in these patients. [Extracted from the article]

Background: Platelet (PLT) transfusions are an essential treatment for bleeding disorders. However, immunologic complications can occur, including alloantibody production against Class I HLA molecules. The principal source of HLA molecules in PLT concentrates (PCs) is the PLTs themselves. However, extracellular microparticles (MPs) present in PCs may express HLA molecules.Study Design and Methods: We used nanoscale flow cytometry to explore the expression of HLA-A2, HLA-B7, and HLA-B57 on the surface of cells, PLT-derived MPs (PMPs), lymphocyte-derived MPs (LMPs), and monocyte-derived MPs (MMPs) present in PCs. Expression was studied during 7 days of storage.Results: Platelets were not the only source of HLA molecules in PCs. HLA molecules were present on PMPs, LMPs, and MMPs. The level of HLA Class I molecule expression varied between haplotypes and MPs of different origins and during storage.Conclusion: Platelets or residual cells remaining after leukoreduction are not the only source of HLA Class I molecules in PCs, highlighting the contribution of MPs to alloimmunization mechanisms. These data may be relevant for the development of new transfusion guidelines. [ABSTRACT FROM AUTHOR]

Background: Patients with hematologic malignancies require prophylactic or curative platelet transfusions to prevent or treat bleeding. Treatments such as chemotherapy, radiotherapy, and hematopoietic stem cell transplantation cause persistent thrombocytopenia, necessitating platelet transfusions. However, class I HLA antibodies can cause a serious complication: immune‐mediated platelet refractoriness. The mechanisms of alloimmunization are incompletely understood. We explored the immunogenicity of HLA molecules and the phenotype of the HLA‐specific CD4+ T cells involved in alloimmunization. Study Design and Methods: We investigated the role of HLA molecules in platelet transfusion immunogenicity in a retrospective cohort study on men with specific anti‐HLA who had undergone transfusion. We investigated the presence and phenotypic profile of HLA‐specific CD4+ T cells in alloimmunized patients included in long‐term platelet transfusion programs for hematologic malignancies. Results: More than 50% of the transfused subjects displayed an antibody response against HLA‐B57 or ‐B58. HLA‐B57–specific CD4+ T‐cell responses were observed in patients alloimmunized against HLA‐B57. Following specific stimulation, the patients presented HLA‐specific CD4+ T cells producing tumor necrosis factor‐α, interleukin (IL)‐13, IL‐17A, IL‐2, IL‐10, and IL‐21. Conclusion: These results shed light on posttransfusion class I anti‐HLA alloimmunization mechanisms and constitute a first step toward developing new strategies for reducing refractoriness. [ABSTRACT FROM AUTHOR]

Alloimmunization against red blood cells (RBCs) is the main immunological risk associated with transfusion in patients with sickle cell disease (SCD). However, about 50-70% of SCD patients never get immunized despite frequent transfusion. In murine models, CD4+ T cells play a key role in RBC alloimmunization. We therefore explored and compared the CD4+ T-cell phenotypes and functions between a group of SCD patients ( n = 11) who never became immunized despite a high transfusion regimen and a group of SCD patients ( n = 10) who had become immunized (at least against Kidd antigen b) after a low transfusion regimen. We studied markers of CD4+ T-cell function, including TLR, that directly control lymphocyte function, and their spontaneous cytokine production. We also tested responders for the cytokine profile in response to Kidd antigen b peptides. Low TLR2/TLR3 expression and, unexpectedly, strong expression of CD40 on CD4+ T cells were associated with the nonresponder status, whereas spontaneous expression of IL-10 by CD4+ T cells and weak Tbet expression were associated with the responder status. A Th17 profile was predominant in responders when stimulated by Jbk. These findings implicate CD4+ T cells in alloimmunization in humans and suggest that they may be exploited to differentiate responders from nonresponders. [ABSTRACT FROM AUTHOR]

HIV controllers are rare individuals who spontaneously control HIV replication in the absence of antiretroviral treatment. Emerging evidence indicates that HIV control is mediated through very active cellular immune responses, though how such responses can persist over time without immune exhaustion is not yet understood. To investigate the nature of memory CD4+ T cells responsible for long-term anti-HIV responses, we characterized the growth kinetics, Vβ repertoire, and avidity for antigen of patient-derived primary CD4+ T cell lines. Specific cell lines were obtained at a high rate for both HIV controllers (16/17) and efficiently treated patients (19/20) in response to the immunodominant Gag293 peptide. However, lines from controllers showed faster growth kinetics than those of treated patients. After normalizing for growth rates, IFN-γ responses directed against the immunodominant Gag293 peptide showed higher functional avidity in HIV controllers, indicating differentiation into highly efficient effector cells. In contrast, responses to Gag161, Gag263, or CMV peptides did not differ between groups. Gag293-specific CD4+ T cells were characterized by a diverse Vβ repertoire, suggesting that multiple clones contributed to the high avidity CD4+ T cell population in controllers. The high functional avidity of the Gag293-specific response could be explained by a high avidity interaction between the TCR and the peptide-MHC complex, as demonstrated by MHC class II tetramer binding. Thus, HIV controllers harbor a pool of memory CD4+ T cells with the intrinsic ability to recognize minimal amounts of Gag antigen, which may explain how they maintain an active antiviral response in the face of very low viremia. [ABSTRACT FROM AUTHOR]