Browsing by Subject "Receptors, Antigen, B-Cell"

Now showing 1 - 5 of 5
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    CD20 deficiency in humans results in impaired T cell-independent antibody responses.
    (J Clin Invest, 2010-01) Kuijpers, Taco W; Bende, Richard J; Baars, Paul A; Grummels, Annette; Derks, Ingrid AM; Dolman, Koert M; Beaumont, Tim; Tedder, Thomas F; van Noesel, Carel JM; Eldering, Eric; van Lier, René AW
    CD20 was the first B cell differentiation antigen identified, and CD20-specific mAbs are commonly used for the treatment of B cell malignancies and autoantibody-mediated autoimmune diseases. Despite this the role of CD20 in human B cell physiology has remained elusive. We describe here a juvenile patient with CD20 deficiency due to a homozygous mutation in a splice junction of the CD20 gene (also known as MS4A1) that results in "cryptic" splicing and nonfunctional mRNA species. Analysis of this patient has led us to conclude that CD20 has a central role in the generation of T cell-independent (TI) antibody responses. Key evidence to support this conclusion was provided by the observation that although antigen-independent B cells developed normally in the absence of CD20 expression, antibody formation, particularly after vaccination with TI antigens, was strongly impaired in the patient. Consistent with this, TI antipolysaccharide B cell responses were severely impeded in CD20-deficient mice. Our study therefore identifies what we believe to be a novel type of humoral immunodeficiency caused by CD20 deficiency and characterized by normal development of antigen-independent B cells, along with a reduced capacity to mount proper antibody responses.
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    Heightened TLR7 signaling primes BCR-activated B cells in chronic graft-versus-host disease for effector functions.
    (Blood advances, 2024-02) Bracken, Sonali J; Suthers, Amy N; DiCioccio, Rachel A; Su, Hsuan; Anand, Sarah; Poe, Jonathan C; Jia, Wei; Visentin, Jonathan; Basher, Fahmin; Jordan, Collin Z; McManigle, William C; Li, Zhiguo; Hakim, Frances T; Pavletic, Steven Z; Bhuiya, Nazmim S; Ho, Vincent T; Horwitz, Mitchell E; Chao, Nelson J; Sarantopoulos, Stefanie

    Abstract

    Chronic graft-versus-host disease (cGVHD) is a debilitating, autoimmune-like syndrome that can occur after allogeneic hematopoietic stem cell transplantation. Constitutively activated B cells contribute to ongoing alloreactivity and autoreactivity in patients with cGVHD. Excessive tissue damage that occurs after transplantation exposes B cells to nucleic acids in the extracellular environment. Recognition of endogenous nucleic acids within B cells can promote pathogenic B-cell activation. Therefore, we hypothesized that cGVHD B cells aberrantly signal through RNA and DNA sensors such as Toll-like receptor 7 (TLR7) and TLR9. We found that B cells from patients and mice with cGVHD had higher expression of TLR7 than non-cGVHD B cells. Using ex vivo assays, we found that B cells from patients with cGVHD also demonstrated increased interleukin-6 production after TLR7 stimulation with R848. Low-dose B-cell receptor (BCR) stimulation augmented B-cell responses to TLR7 activation. TLR7 hyperresponsiveness in cGVHD B cells correlated with increased expression and activation of the downstream transcription factor interferon regulatory factor 5. Because RNA-containing immune complexes can activate B cells through TLR7, we used a protein microarray to identify RNA-containing antigen targets of potential pathological relevance in cGVHD. We found that many of the unique targets of active cGVHD immunoglobulin G (IgG) were nucleic acid-binding proteins. This unbiased assay identified the autoantigen and known cGVHD target Ro-52, and we found that RNA was required for IgG binding to Ro-52. Herein, we find that BCR-activated B cells have aberrant TLR7 signaling responses that promote potential effector responses in cGVHD.
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    IGHV1-69 B cell chronic lymphocytic leukemia antibodies cross-react with HIV-1 and hepatitis C virus antigens as well as intestinal commensal bacteria.
    (PLoS One, 2014) Hwang, Kwan-Ki; Trama, Ashley M; Kozink, Daniel M; Chen, Xi; Wiehe, Kevin; Cooper, Abby J; Xia, Shi-Mao; Wang, Minyue; Marshall, Dawn J; Whitesides, John; Alam, Munir; Tomaras, Georgia D; Allen, Steven L; Rai, Kanti R; McKeating, Jane; Catera, Rosa; Yan, Xiao-Jie; Chu, Charles C; Kelsoe, Garnett; Liao, Hua-Xin; Chiorazzi, Nicholas; Haynes, Barton F
    B-cell chronic lymphocytic leukemia (B-CLL) patients expressing unmutated immunoglobulin heavy variable regions (IGHVs) use the IGHV1-69 B cell receptor (BCR) in 25% of cases. Since HIV-1 envelope gp41 antibodies also frequently use IGHV1-69 gene segments, we hypothesized that IGHV1-69 B-CLL precursors may contribute to the gp41 B cell response during HIV-1 infection. To test this hypothesis, we rescued 5 IGHV1-69 unmutated antibodies as heterohybridoma IgM paraproteins and as recombinant IgG1 antibodies from B-CLL patients, determined their antigenic specificities and analyzed BCR sequences. IGHV1-69 B-CLL antibodies were enriched for reactivity with HIV-1 envelope gp41, influenza, hepatitis C virus E2 protein and intestinal commensal bacteria. These IGHV1-69 B-CLL antibodies preferentially used IGHD3 and IGHJ6 gene segments and had long heavy chain complementary determining region 3s (HCDR3s) (≥21 aa). IGHV1-69 B-CLL BCRs exhibited a phenylalanine at position 54 (F54) of the HCDR2 as do rare HIV-1 gp41 and influenza hemagglutinin stem neutralizing antibodies, while IGHV1-69 gp41 antibodies induced by HIV-1 infection predominantly used leucine (L54) allelic variants. These results demonstrate that the B-CLL cell population is an expansion of members of the innate polyreactive B cell repertoire with reactivity to a number of infectious agent antigens including intestinal commensal bacteria. The B-CLL IGHV1-69 B cell usage of F54 allelic variants strongly suggests that IGHV1-69 B-CLL gp41 antibodies derive from a restricted B cell pool that also produces rare HIV-1 gp41 and influenza hemagglutinin stem antibodies.
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    Single-cell landscape analysis unravels molecular programming of the human B cell compartment in chronic GVHD.
    (JCI insight, 2023-06) Poe, Jonathan C; Fang, Jiyuan; Zhang, Dadong; Lee, Marissa R; DiCioccio, Rachel A; Su, Hsuan; Qin, Xiaodi; Zhang, Jennifer Y; Visentin, Jonathan; Bracken, Sonali J; Ho, Vincent T; Wang, Kathy S; Rose, Jeremy J; Pavletic, Steven Z; Hakim, Frances T; Jia, Wei; Suthers, Amy N; Curry-Chisolm, Itaevia M; Horwitz, Mitchell E; Rizzieri, David A; McManigle, William C; Chao, Nelson J; Cardones, Adela R; Xie, Jichun; Owzar, Kouros; Sarantopoulos, Stefanie
    Alloreactivity can drive autoimmune syndromes. After allogeneic hematopoietic stem cell transplantation (allo-HCT), chronic graft-versus-host disease (cGVHD), a B cell-associated autoimmune-like syndrome, commonly occurs. Because donor-derived B cells continually develop under selective pressure from host alloantigens, aberrant B cell receptor (BCR) activation and IgG production can emerge and contribute to cGVHD pathobiology. To better understand molecular programing of B cells in allo-HCT, we performed scRNA-Seq analysis on high numbers of purified B cells from patients. An unsupervised analysis revealed 10 clusters, distinguishable by signature genes for maturation, activation, and memory. Within the memory B cell compartment, we found striking transcriptional differences in allo-HCT patients compared with healthy or infected individuals, including potentially pathogenic atypical B cells (ABCs) that were expanded in active cGVHD. To identify intrinsic alterations in potentially pathological B cells, we interrogated all clusters for differentially expressed genes (DEGs) in active cGVHD versus patients who never had signs of immune tolerance loss (no cGVHD). Active cGVHD DEGs occurred in both naive and BCR-activated B cell clusters. Remarkably, some DEGs occurred across most clusters, suggesting common molecular programs that may promote B cell plasticity. Our study of human allo-HCT and cGVHD provides understanding of altered B cell memory during chronic alloantigen stimulation.
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    Very low affinity B cells form germinal centers, become memory B cells, and participate in secondary immune responses when higher affinity competition is reduced.
    (J Exp Med, 2002-05-06) Dal Porto, Joseph M; Haberman, Ann M; Kelsoe, Garnett; Shlomchik, Mark J
    To understand the relationship between the affinity of the B cell antigen receptor (BCR) and the immune response to antigen, two lines of immunoglobulin H chain transgenic (Tg) mice were created. H50Gmu(a) and T1(V23)mu(a) mice express mu H chain transgenes that associate with the lambda1 L chains to bind the (4-hydroxy-3-nitrophenyl)acetyl hapten with association constants (K(a)s) of only 1.2 x 10(5) M(-1) and 3 x 10(4) M(-1), respectively. Both lines mounted substantial antibody-forming cell (AFC) and germinal center (GC) responses. H50Gmu(a) Tg mice also generated memory B cells. T1(V23)mu(a) B cells formed AFC and GCs, but were largely replaced in late GCs by antigen-specific cells that express endogenous BCRs. Thus, B lymphocytes carrying BCRs with affinities previously thought to be irrelevant in specific immune responses are in fact capable of complete T cell-dependent immune responses when relieved of substantial competition from other B cells. The failure to observe such B cells normally in late primary responses and in memory B cell populations is the result of competition, rather than an intrinsic inability of low affinity B cells.