335 research outputs found
Correction to: A Novel Case of IFNAR1 Deficiency Identified a Common Canonical Splice Site Variant in DOCK8 in Western Polynesia: The Importance of Validating Variants of Unknown Significance in Under-Represented Ancestries
No full textIn this article, Alberto Pinzon-Charry, Cindy S Ma and Stuart G. Tangye should have been denoted as equally contributing authors. The original version has been corrected
Impact of SARS-CoV-2 infection and COVID-19 on patients with inborn errors of immunity
No full text: Since the arrival of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in December 2019, its characterization as a novel human pathogen, and the resulting coronavirus disease 2019 (COVID-19) pandemic, over 6.5 million people have died worldwide-a stark and sobering reminder of the fundamental and nonredundant roles of the innate and adaptive immune systems in host defense against emerging pathogens. Inborn errors of immunity (IEI) are caused by germline variants, typically in single genes. IEI are characterized by defects in development and/or function of cells involved in immunity and host defense, rendering individuals highly susceptible to severe, recurrent, and sometimes fatal infections, as well as immune dysregulatory conditions such as autoinflammation, autoimmunity, and allergy. The study of IEI has revealed key insights into the molecular and cellular requirements for immune-mediated protection against infectious diseases. Indeed, this has been exemplified by assessing the impact of SARS-CoV-2 infection in individuals with previously diagnosed IEI, as well as analyzing rare cases of severe COVID-19 in otherwise healthy individuals. This approach has defined fundamental aspects of mechanisms of disease pathogenesis, immunopathology in the context of infection with a novel pathogen, and therapeutic options to mitigate severe disease. This review summarizes these findings and illustrates how the study of these rare experiments of nature can inform key features of human immunology, which can then be leveraged to improve therapies for treating emerging and established infectious diseases
Activated PI3Kδ breaches multiple B cell tolerance checkpoints and causes autoantibody production
No full textAntibody-mediated autoimmune diseases are a major health burden. However, our understanding of how self-reactive B cells escape self-tolerance checkpoints to secrete pathogenic autoantibodies remains incomplete. Here, we demonstrate that patients with monogenic immune dysregulation caused by gain-of-function mutations in PIK3CD, encoding the p110δ catalytic subunit of phosphoinositide 3-kinase (PI3K), have highly penetrant secretion of autoreactive IgM antibodies. In mice with the corresponding heterozygous Pik3cd activating mutation, self-reactive B cells exhibit a cell-autonomous subversion of their response to self-antigen: instead of becoming tolerized and repressed from secreting autoantibody, Pik3cd gain-of-function B cells are activated by self-antigen to form plasmablasts that secrete high titers of germline-encoded IgM autoantibody and hypermutating germinal center B cells. However, within the germinal center, peripheral tolerance was still enforced, and there was selection against B cells with high affinity for self-antigen. These data show that the strength of PI3K signaling is a key regulator of pregerminal center B cell self-tolerance and thus represents a druggable pathway to treat antibody-mediated autoimmunity.sponsorship: This work was supported by National Health and Medical Research Council (NHMRC) program grants (1016953 and 1113904 to S.G. Tangye, R. Brink, and C.C. Goodnow), NHMRC project grants (1088215 to E.K. Deenick; 1127157 to S.G. Tangye and E.K. Deenick), NHMRC Principal Research Fellowships (1042925 to S.G. Tangye; 1105877 to R. Brink), a Fulbright Senior Scholarship (to S.G. Tangye), the Office of Health and Medical Research of the New South Wales Government, the Jeffrey Modell Foundation, the John Brown Cook Foundation, the Ross Trust, and a Bench-to-Bedside grant from the National Institute of Allergy and Infectious Diseases, National Institutes of Health. G. Uzel and L.D. Notarangelo are supported by the Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health. (National Health and Medical Research Council (NHMRC)|1016953, National Health and Medical Research Council (NHMRC)|1113904, NHMRC|1088215, NHMRC|1127157, NHMRC|1042925, NHMRC|1105877, Fulbright Senior Scholarship, Office of Health and Medical Research of the New South Wales Government, Jeffrey Modell Foundation, John Brown Cook Foundation, Ross Trust, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, National Institute of Allergy and Infectious Diseases|ZIAAI001222, National Health and Medical Research Council of Australia|1088215, National Health and Medical Research Council of Australia|1127157, National Health and Medical Research Council of Australia|1105877)status: Publishe
In Vitro Regulation of Growth, Differentiation and Survival of Leukemic CD5+ B Cells
No full textUniversity of Technology, Sydney. Faculty of Science.B cell chronic lymphocytic leukemia (B-CLL) is a hematologic neoplasm characterised by the proliferation and accumulation of sIgM+/D+ B cells that fail to progress to the final stages of B cell development. The malignant cells in B-CLL also express the pan-T cell antigen CD5, suggesting that CLL is a malignancy of the CD5+ subset of B cells. Additional characteristics of the malignant clone include a low proliferative index, enhanced in vivo survival and constitutive expression of the anti-apoptosis oncoprotein bcl-2. The behaviour of leukemic CD5 B cells in vitro contrasts their arrested in vivo state. That is, despite the majority of cells being arrested in the G0 phase of the cell cycle, the leukemic B cells are not irreversibly frozen as they can be induced to differentiate to Ig-secreting cells under appropriate in vitro conditions. Furthermore, leukemic CD5 B cells rapidly undergo death by apoptosis following in vitro culture. This thesis describes the requirements for in vitro activation of leukemic CD5+ B cells, the characterisation of the events involved in apoptosis of these cells as well as the identification of various growth factors capable of modulating these events.
Stimulation of unfractionated peripheral blood lymphocytes (PBLs) from three patients with B-CLL with the phorbol ester PMA and the mitogens PHA and PWM resulted in significant increases in cell proliferation, RNA synthesis and 1gM secretion when compared to unstimulated cell populations. PMA was the most potent inducer of 1gM secretion and this occurred irrespective of the presence of residual T cells. PMA-induced proliferation and RNA synthesis were also independent of T cells. However, in the presence of T cells, these parameters of cellular activation were enhanced during in vitro culture. Thus, the inductive ability of PMA on leukemic CD5 B cells was independent of T cells. In contrast, activation and differentiation of the leukemic CD5 B cells into 1gM-secreting cells following culture with mitogens did not occur in the absence of T cells. Interestingly, co-stimulation of leukemic CD5+ B cells with PMA and anti-Ig induced cellular responses that exceeded those induced by either activator alone. Thus, leukemic CD5+ B cells from patients with B-CLL can be activated in vitro and differentiate in response to stimulation via both T cell-dependent and T cell-independent mechanisms.
Apoptotic cell death was characterised in purified leukemic CD5 B cells obtained from six B-CLL patients. All leukemic CD5 B cell populations entered an apoptotic pathway in vitro as evidenced by a reduction in cell size, loss of cell viability and fragmentation of DNA into multimers of -180 base pairs. Following 24 hours of in vitro culture 24.0±16% of DNA was fragmented. After 8 days, the majority of DNA was fragmented, and fewer than 10% of cultured cells were viable. Examination of bcl-2 expression in the malignant B cells by flow cytometry revealed a unimodal pattern of expression in greater than 85% of cells from each B-CLL patient prior to culture. During in vitro culture, bcl-2 expression became bimodal such that the B cells displayed a bcl-2hjgh and bcl-2iow phenotype. The level of expression by the bCl2hjgh cells was similar to that observed prior to in vitro culture, indicating that bcl-2 is down-regulated in apoptosing cells. Interestingly, despite this downregulation, the overall number of cells positive for bcl-2 remained constant. This suggests that the enhanced survival of leukemic CD5+ B cells in vivo is mediated by the sustained expression of bcl-2 and that additional mechanisms exist capable of overriding the protective effect of bcl-2 when bcl-2 is present at reduced levels. Leukemic B cell apoptosis has previously been reported to be delayed or prevented by IL-4, IFN-y and IFN-a. These results were confirmed in this study where it was found that culture of leukemic CD5 B cells with IL-4 or IFN-y enhanced cell viability and delayed apoptosis in 6/6 and 5/6 populations of leukemic B cells, respectively. This function was also found to be shared by IL-2, IL-6, IL-13 and TNF-a as these cytokines enhanced cell viability and delayed apoptosis in some of the cell populations examined at a level similar to that observed for IL-4 and IFN-y. These cytokines may mediate their effect via the expression of bcl2 as culture in the presence of IL-2, IL-4, IL-6, IL-13, IFN-y or TNF-a resulted in a higher percentage of cells displaying the bcl-2high phenotype, compared to unstimulated cells. Taken together, these results suggest that autocrine and/or paracrine growth loops may play a role in the pathogenesis of B-CLL and that cytokines that prevent apoptosis in vitro may be targets for treatment of this B cell malignancy
Plasmacytoid DCs Induce Gutsy Plasma Cells
No full textImmunoglobulin (Ig) A is critical for protective immune responses at mucosal surfaces. In this issue of Immunity, Tezuka et al. (2011) identify an important relay between stromal cells and plasmacytoid dendritic cells that regulates IgA production by murine B cells
Cytokine-mediated regulation of plasma cell generation: IL-21 takes center stage
No full textDuring our life we are surrounded by continuous threats from a diverse range of invading pathogens. Our immune system has evolved multiple mechanisms to efficiently deal with these threats to prevent them causing disease. Differentiation of mature B cells into plasma cells (PC) - the antibody (Ab) secreting cells of the immune system - is critical for the generation of protective and long-lived humoral immune responses. Indeed, efficient production of antigen (Ag)-specific Ab underlies the success of most currently available vaccines. The mature B cell pool is composed of several subsets, distinguished from one according to size, surface marker expression, location and Ag exposure, and they all have the capacity to differentiate into PCs. For a B cell to acquire the capacity to produce Abs, it must undergo an extensive differentiation process driven by changes in gene expression. Two broad categories of Ag exist that cause B cell activation and differentiation: T cell dependent (TD) or T cell independent (TI). In addition to the B cell subset and nature of the Ag, it is important to consider the cytokine environment that also influences how B cell differentiation is achieved. Thus, while many cytokines can induce Ab secretion by B cells after activation with mimics of TD and TI stimuli in vitro, they can have different efficacies and specificities, and can often preferentially induce production of one Ig isotype over another. Here, we will provide an overview of in vitro studies (mouse and human origin) that evaluated the role the different cytokines in inducing the differentiation of distinct B cell subsets to the PC lineage. We will place particular emphasis on IL-21, which has emerged as the most potent inducer of terminal B cell differentiation in humans. We will also focus on the role of IL-21 and defects in B-cell function and how these contribute to human immunopathologies such as primary immunodeficiencies and B-cell mediated autoimmune conditions
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