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Beyer H, Sommerfeld M, Grandien K, Faust C, Tillmann B, Leuschner WD, Régnier-Vigouroux A, Weil S, Rao E, Langer T. Functional studies with IgM and IgA immunoglobulins: binding to pIgR, FcαμR, FcμR, and CDC activities. APMIS 2024; 132:277-288. [PMID: 38232051 DOI: 10.1111/apm.13377] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2023] [Accepted: 01/02/2024] [Indexed: 01/19/2024]
Abstract
IgMs are the first antibodies produced by the immune system upon encounter of a possible pathogen and are one of five antibody subclasses in humans. For IgG, the most intensively studied antibody class, the N-linked glycosylation site located in the Fc-domain is directly involved in high affinity binding to the respective receptors and initiation of corresponding immune response. IgM molecules have five N-glycosylation sites and one N-glycosylation site in the J-chain, which can be incorporated in IgM or IgA molecules. There is only limited knowledge available concerning the function of these N-glycosylations in IgMs. To address this question, we produced IgM molecules lacking a particular N-glycosylation site and tested these variants as well as IgA molecules for binding to the known receptors: the polymeric immunoglobulin receptor (pIgR), the dual receptor for IgA and IgM, FcαμR, and the specific receptor for IgM, FcμR. The single glycosylation sites did not show an impact on expression and multimerization, except for variant N402Q, which could not be expressed. In SPR measurements, no major impact on the binding to the receptors by particular glycosylation sites could be detected. In cellular assays, deglycosylated variants showed some alterations in induction of CDC activity. Most strikingly, we observed also binding of IgA to the FcμR in the same affinity range as IgM, suggesting that this might have a physiological role. To further substantiate the binding of IgA to FcμR we used IgA from different origins and were able to confirm binding of IgA preparations to the FcμR.
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Affiliation(s)
- Hanna Beyer
- Sanofi-Aventis Deutschland GmbH, R&D Large Molecules Research, Frankfurt am Main, Germany
- Institute for Developmental Biology and Neurobiology (IDN), Johannes Gutenberg University, Mainz, Germany
| | - Mark Sommerfeld
- Sanofi-Aventis Deutschland GmbH, R&D Large Molecules Research, Frankfurt am Main, Germany
| | - Kaj Grandien
- Sanofi-Aventis Deutschland GmbH, R&D Large Molecules Research, Frankfurt am Main, Germany
| | - Christine Faust
- Sanofi-Aventis Deutschland GmbH, R&D Large Molecules Research, Frankfurt am Main, Germany
| | - Bodo Tillmann
- Sanofi-Aventis Deutschland GmbH, R&D Large Molecules Research, Frankfurt am Main, Germany
| | - Wulf Dirk Leuschner
- Sanofi-Aventis Deutschland GmbH, R&D Large Molecules Research, Frankfurt am Main, Germany
| | - Anne Régnier-Vigouroux
- Institute for Developmental Biology and Neurobiology (IDN), Johannes Gutenberg University, Mainz, Germany
| | - Sandra Weil
- Sanofi-Aventis Deutschland GmbH, R&D Large Molecules Research, Frankfurt am Main, Germany
| | - Ercole Rao
- Sanofi-Aventis Deutschland GmbH, R&D Large Molecules Research, Frankfurt am Main, Germany
| | - Thomas Langer
- Sanofi-Aventis Deutschland GmbH, R&D Large Molecules Research, Frankfurt am Main, Germany
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2
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Kubagawa H, Skopnik CM, Al-Qaisi K, Calvert RA, Honjo K, Kubagawa Y, Teuber R, Aliabadi PM, Enghard P, Radbruch A, Sutton BJ. Differences between Human and Mouse IgM Fc Receptor (FcµR). Int J Mol Sci 2021; 22:ijms22137024. [PMID: 34209905 PMCID: PMC8267714 DOI: 10.3390/ijms22137024] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2021] [Revised: 06/23/2021] [Accepted: 06/25/2021] [Indexed: 01/02/2023] Open
Abstract
Both non-immune "natural" and antigen-induced "immune" IgM are important for protection against pathogens and for regulation of immune responses to self-antigens. Since the bona fide IgM Fc receptor (FcµR) was identified in humans by a functional cloning strategy in 2009, the roles of FcµR in these IgM effector functions have begun to be explored. In this short essay, we describe the differences between human and mouse FcµRs in terms of their identification processes, cellular distributions and ligand binding activities with emphasis on our recent findings from the mutational analysis of human FcµR. We have identified at least three sites of human FcµR, i.e., Asn66 in the CDR2, Lys79 to Arg83 in the DE loop and Asn109 in the CDR3, responsible for its constitutive IgM-ligand binding. Results of computational structural modeling analysis are consistent with these mutational data and a model of the ligand binding, Ig-like domain of human FcµR is proposed. Serendipitously, substitution of Glu41 and Met42 in the CDR1 of human FcµR with mouse equivalents Gln and Leu, either single or more prominently in combination, enhances both the receptor expression and IgM binding. These findings would help in the future development of preventive and therapeutic interventions targeting FcµR.
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Affiliation(s)
- Hiromi Kubagawa
- Deutsches Rheuma-Forschungszentrum, 10117 Berlin, Germany; (C.M.S.); (K.A.-Q.); (R.T.); (P.M.A.); (A.R.)
- Correspondence: ; Tel.: +49-030-2846-0782
| | - Christopher M. Skopnik
- Deutsches Rheuma-Forschungszentrum, 10117 Berlin, Germany; (C.M.S.); (K.A.-Q.); (R.T.); (P.M.A.); (A.R.)
| | - Khlowd Al-Qaisi
- Deutsches Rheuma-Forschungszentrum, 10117 Berlin, Germany; (C.M.S.); (K.A.-Q.); (R.T.); (P.M.A.); (A.R.)
| | - Rosaleen A. Calvert
- Randall Centre for Cell and Molecular Biophysics, King’s College, London SE1 1UL, UK; (R.A.C.); (B.J.S.)
| | - Kazuhito Honjo
- Department of Pathology of University of Alabama at Birmingham, Birmingham, AL 35294, USA.; (K.H.); (Y.K.)
| | - Yoshiki Kubagawa
- Department of Pathology of University of Alabama at Birmingham, Birmingham, AL 35294, USA.; (K.H.); (Y.K.)
| | - Ruth Teuber
- Deutsches Rheuma-Forschungszentrum, 10117 Berlin, Germany; (C.M.S.); (K.A.-Q.); (R.T.); (P.M.A.); (A.R.)
| | - Pedram Mahmoudi Aliabadi
- Deutsches Rheuma-Forschungszentrum, 10117 Berlin, Germany; (C.M.S.); (K.A.-Q.); (R.T.); (P.M.A.); (A.R.)
| | - Philipp Enghard
- Department of Nephrology and Medical Intensive Care, Charité-Universitätmedizin, 10117 Berlin, Germany;
| | - Andreas Radbruch
- Deutsches Rheuma-Forschungszentrum, 10117 Berlin, Germany; (C.M.S.); (K.A.-Q.); (R.T.); (P.M.A.); (A.R.)
| | - Brian J. Sutton
- Randall Centre for Cell and Molecular Biophysics, King’s College, London SE1 1UL, UK; (R.A.C.); (B.J.S.)
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3
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Bohländer F, Riehl D, Weißmüller S, Gutscher M, Schüttrumpf J, Faust S. Immunomodulation: Immunoglobulin Preparations Suppress Hyperinflammation in a COVID-19 Model via FcγRIIA and FcαRI. Front Immunol 2021; 12:700429. [PMID: 34177967 PMCID: PMC8223875 DOI: 10.3389/fimmu.2021.700429] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2021] [Accepted: 05/21/2021] [Indexed: 12/13/2022] Open
Abstract
The rapid spread of SARS-CoV-2 has induced a global pandemic. Severe forms of COVID-19 are characterized by dysregulated immune response and "cytokine storm". The role of IgG and IgM antibodies in COVID-19 pathology is reasonably well studied, whereas IgA is neglected. To improve clinical outcome of patients, immune modulatory drugs appear to be beneficial. Such drugs include intravenous immunoglobulin preparations, which were successfully tested in severe COVID-19 patients. Here we established a versatile in vitro model to study inflammatory as well as anti-inflammatory processes by therapeutic human immunoglobulins. We dissect the inflammatory activation on neutrophil-like HL60 cells, using an immune complex consisting of latex beads coated with spike protein of SARS-CoV-2 and opsonized with specific immunoglobulins from convalescent plasma. Our data clarifies the role of Fc-receptor-dependent phagocytosis via IgA-FcαRI and IgG-FcγR for COVID-19 disease followed by cytokine release. We show that COVID-19 associated inflammation could be reduced by addition of human immunoglobulin preparations (IVIG and trimodulin), while trimodulin elicits stronger immune modulation by more powerful ITAMi signaling. Besides IgG, the IgA component of trimodulin in particular, is of functional relevance for immune modulation in this assay setup, highlighting the need to study IgA mediated immune response.
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Affiliation(s)
- Fabian Bohländer
- Department of Analytical Development and Validation, Corporate R&D, Biotest AG, Dreieich, Germany
- Corporate R&D, Biotest AG, Dreieich, Germany
| | - Dennis Riehl
- Department of Analytical Development and Validation, Corporate R&D, Biotest AG, Dreieich, Germany
- Corporate R&D, Biotest AG, Dreieich, Germany
| | - Sabrina Weißmüller
- Corporate R&D, Biotest AG, Dreieich, Germany
- Department of Translational Research, Preclinical Research, Corporate R&D, Biotest AG, Dreieich, Germany
| | - Marcus Gutscher
- Department of Analytical Development and Validation, Corporate R&D, Biotest AG, Dreieich, Germany
- Corporate R&D, Biotest AG, Dreieich, Germany
| | | | - Stefanie Faust
- Department of Analytical Development and Validation, Corporate R&D, Biotest AG, Dreieich, Germany
- Corporate R&D, Biotest AG, Dreieich, Germany
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4
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Skopnik CM, Al-Qaisi K, Calvert RA, Enghard P, Radbruch A, Sutton BJ, Kubagawa H. Identification of Amino Acid Residues in Human IgM Fc Receptor (FcµR) Critical for IgM Binding. Front Immunol 2021; 11:618327. [PMID: 33584711 PMCID: PMC7873564 DOI: 10.3389/fimmu.2020.618327] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2020] [Accepted: 12/03/2020] [Indexed: 11/17/2022] Open
Abstract
Both non-immune “natural” and antigen-induced “immune” IgM are important for protection against infections and for regulation of immune responses to self-antigens. The roles of its Fc receptor (FcµR) in these IgM effector functions have begun to be explored. In the present study, by taking advantage of the difference in IgM-ligand binding of FcµRs of human (constitutive binding) and mouse (transient binding), we replaced non-conserved amino acid residues of human FcµR with mouse equivalents before establishment of cell lines stably expressing mutant or wild-type (WT) receptors. The resultant eight-different mutant FcµR-bearing cells were compared with WT receptor-bearing cells for cell-surface expression and IgM-binding by flow cytometric assessments using receptor-specific mAbs and IgM paraproteins as ligands. Three sites Asn66, Lys79-Arg83, and Asn109, which are likely in the CDR2, DE loop and CDR3 of the human FcµR Ig-like domain, respectively, were responsible for constitutive IgM binding. Intriguingly, substitution of Glu41 and Met42 in the presumed CDR1 with the corresponding mouse residues Gln and Leu, either single or more prominently in combination, enhanced both the receptor expression and IgM binding. A four-aa stretch of Lys24-Gly27 in the predicted A ß-strand of human FcµR appeared to be essential for maintenance of its proper receptor conformation on plasma membranes because of reduction of both receptor expression and IgM-binding potential when these were mutated. Results from a computational structural modeling analysis were consistent with these mutational data and identified a possible mode of binding of FcµR with IgM involving the loops including Asn66, Arg83 and Asn109 of FcµR interacting principally with the Cµ4 domain including Gln510 and to a lesser extent Cµ3 domain including Glu398, of human IgM. To our knowledge, this is the first experimental report describing the identification of amino acid residues of human FcµR critical for binding to IgM Fc.
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Affiliation(s)
| | - Khlowd Al-Qaisi
- Humoral Immune Regulation, Deutsches Rheuma-Forschungszentrum, Berlin, Germany
| | - Rosaleen A Calvert
- Randall Centre for Cell and Molecular Biophysics, King's College London, London, United Kingdom
| | - Philipp Enghard
- Department of Nephrology and Medical Intensive Care, Charité-Universitätmedizin, Berlin, Germany
| | - Andreas Radbruch
- Humoral Immune Regulation, Deutsches Rheuma-Forschungszentrum, Berlin, Germany
| | - Brian J Sutton
- Randall Centre for Cell and Molecular Biophysics, King's College London, London, United Kingdom
| | - Hiromi Kubagawa
- Humoral Immune Regulation, Deutsches Rheuma-Forschungszentrum, Berlin, Germany
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5
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Li Y, Wang G, Li N, Wang Y, Zhu Q, Chu H, Wu W, Tan Y, Yu F, Su XD, Gao N, Xiao J. Structural insights into immunoglobulin M. Science 2020; 367:1014-1017. [PMID: 32029689 DOI: 10.1126/science.aaz5425] [Citation(s) in RCA: 75] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2019] [Accepted: 01/24/2020] [Indexed: 12/21/2022]
Abstract
Immunoglobulin M (IgM) plays a pivotal role in both humoral and mucosal immunity. Its assembly and transport depend on the joining chain (J-chain) and the polymeric immunoglobulin receptor (pIgR), but the underlying molecular mechanisms of these processes are unclear. We report a cryo-electron microscopy structure of the Fc region of human IgM in complex with the J-chain and pIgR ectodomain. The IgM-Fc pentamer is formed asymmetrically, resembling a hexagon with a missing triangle. The tailpieces of IgM-Fc pack into an amyloid-like structure to stabilize the pentamer. The J-chain caps the tailpiece assembly and bridges the interaction between IgM-Fc and the polymeric immunoglobulin receptor, which undergoes a large conformational change to engage the IgM-J complex. These results provide a structural basis for the function of IgM.
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Affiliation(s)
- Yaxin Li
- State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences, Peking University, Beijing, China.,Peking-Tsinghua Center for Life Sciences, Peking University, Beijing, China
| | - Guopeng Wang
- State Key Laboratory of Membrane Biology, School of Life Sciences, Peking University, Beijing, China
| | - Ningning Li
- Peking-Tsinghua Center for Life Sciences, Peking University, Beijing, China.,State Key Laboratory of Membrane Biology, School of Life Sciences, Peking University, Beijing, China
| | - Yuxin Wang
- State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences, Peking University, Beijing, China.,Peking-Tsinghua Center for Life Sciences, Peking University, Beijing, China
| | - Qinyu Zhu
- State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences, Peking University, Beijing, China.,Peking-Tsinghua Center for Life Sciences, Peking University, Beijing, China
| | - Huarui Chu
- State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences, Peking University, Beijing, China.,Peking-Tsinghua Center for Life Sciences, Peking University, Beijing, China
| | - Wenjun Wu
- Renal Division, Department of Medicine, Peking University First Hospital, Beijing, China.,Institute of Nephrology, Peking University, Beijing, China
| | - Ying Tan
- Renal Division, Department of Medicine, Peking University First Hospital, Beijing, China.,Institute of Nephrology, Peking University, Beijing, China
| | - Feng Yu
- Renal Division, Department of Medicine, Peking University First Hospital, Beijing, China.,Institute of Nephrology, Peking University, Beijing, China.,Department of Nephrology, Peking University International Hospital, Beijing, China
| | - Xiao-Dong Su
- State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences, Peking University, Beijing, China
| | - Ning Gao
- Peking-Tsinghua Center for Life Sciences, Peking University, Beijing, China.,State Key Laboratory of Membrane Biology, School of Life Sciences, Peking University, Beijing, China
| | - Junyu Xiao
- State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences, Peking University, Beijing, China. .,Peking-Tsinghua Center for Life Sciences, Peking University, Beijing, China
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6
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Regulation of Humoral Immune Responses and B Cell Tolerance by the IgM Fc Receptor (FcμR). ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2020; 1254:75-86. [DOI: 10.1007/978-981-15-3532-1_7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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7
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Blandino R, Baumgarth N. Secreted IgM: New tricks for an old molecule. J Leukoc Biol 2019; 106:1021-1034. [PMID: 31302940 PMCID: PMC6803036 DOI: 10.1002/jlb.3ri0519-161r] [Citation(s) in RCA: 44] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2019] [Revised: 06/25/2019] [Accepted: 06/26/2019] [Indexed: 12/27/2022] Open
Abstract
Secreted IgM (sIgM) is a multifunctional evolutionary conserved antibody that is critical for the maintenance of tissue homeostasis as well as the development of fully protective humoral responses to pathogens. Constitutive secretion of self- and polyreactive natural IgM, produced mainly by B-1 cells, provides a circulating antibody that engages with autoantigens as well as invading pathogens, removing apoptotic and other cell debris and initiating strong immune responses. Pathogen-induced IgM production by B-1 and conventional B-2 cells strengthens this early, passive layer of IgM-mediated immune defense and regulates subsequent IgG production. The varied effects of secreted IgM on immune homeostasis and immune defense are facilitated through its binding to numerous different cell types via different receptors. Recent studies identified a novel function for pentameric IgM, namely as a transporter for the effector protein ″apoptosis-inhibitor of macrophages″ (AIM/CD5L). This review aims to provide a summary of the known functions and effects of sIgM on immune homeostasis and immune defense, and its interaction with its various receptors, and to highlight the many critical immune regulatory functions of this ancient and fascinating immunoglobulin.
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Affiliation(s)
- Rebecca Blandino
- Biochemistry, Molecular, Cellular and Developmental Biology Graduate Group, University of California, Davis
- Center for Comparative Medicine and University of California, Davis
| | - Nicole Baumgarth
- Biochemistry, Molecular, Cellular and Developmental Biology Graduate Group, University of California, Davis
- Center for Comparative Medicine and University of California, Davis
- Dept. Pathology, Microbiology & Immunology, University of California, Davis
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8
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Kubagawa H, Honjo K, Ohkura N, Sakaguchi S, Radbruch A, Melchers F, Jani PK. Functional Roles of the IgM Fc Receptor in the Immune System. Front Immunol 2019; 10:945. [PMID: 31130948 PMCID: PMC6509151 DOI: 10.3389/fimmu.2019.00945] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2019] [Accepted: 04/12/2019] [Indexed: 12/14/2022] Open
Abstract
It is now evident from studies of mice unable to secrete IgM that both non-immune “natural” and antigen-induced “immune” IgM are important for protection against pathogens and for regulation of immune responses to self-antigens. Since identification of its Fc receptor (FcμR) by a functional cloning strategy in 2009, the roles of FcμR in these IgM effector functions have begun to be explored. Unlike Fc receptors for switched Ig isotypes (e.g., FcγRs, FcεRs, FcαR, Fcα/μR, pIgR, FcRn), FcμR is selectively expressed by lymphocytes: B, T, and NK cells in humans and only B cells in mice. FcμR may have dual signaling ability: one through a potential as yet unidentified adaptor protein non-covalently associating with the FcμR ligand-binding chain via a His in transmembrane segment and the other through its own Tyr and Ser residues in the cytoplasmic tail. FcμR binds pentameric and hexameric IgM with a high avidity of ~10 nM in solution, but more efficiently binds IgM when it is attached to a membrane component via its Fab region on the same cell surface (cis engagement). Four different laboratories have generated Fcmr-ablated mice and eight different groups of investigators have examined the resultant phenotypes. There have been some clear discrepancies reported that appear to be due to factors including differences in the exons of Fcmr that were targeted to generate the knockouts. One common feature among these different mutant mice, however, is their propensity to produce autoantibodies of both IgM and IgG isotypes. In this review, we briefly describe recent findings concerning the functions of FcμR in both mice and humans and propose a model for how FcμR plays a regulatory role in B cell tolerance.
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Affiliation(s)
| | - Kazuhito Honjo
- Department of Medicine, School of Medicine, University of Alabama at Birmingham, Birmingham, AL, United States
| | - Naganari Ohkura
- Immunology Frontier Research Center, Osaka University, Osaka, Japan
| | - Shimon Sakaguchi
- Immunology Frontier Research Center, Osaka University, Osaka, Japan
| | | | | | - Peter K Jani
- Deutsches Rheuma-Forschungszentrum, Berlin, Germany
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9
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Liu J, Wang Y, Xiong E, Hong R, Lu Q, Ohno H, Wang JY. Role of the IgM Fc Receptor in Immunity and Tolerance. Front Immunol 2019; 10:529. [PMID: 30967868 PMCID: PMC6438924 DOI: 10.3389/fimmu.2019.00529] [Citation(s) in RCA: 54] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2018] [Accepted: 02/27/2019] [Indexed: 11/13/2022] Open
Abstract
Immunoglobulin (Ig) M is the first antibody isotype to appear during evolution, ontogeny and immune responses. IgM not only serves as the first line of host defense against infections but also plays an important role in immune regulation and immunological tolerance. For many years, IgM is thought to function by binding to antigen and activating complement system. With the discovery of the IgM Fc receptor (FcμR), it is now clear that IgM can also elicit its function through FcμR. In this review, we will describe the molecular characteristics of FcμR, its role in B cell development, maturation and activation, humoral immune responses, host defense, and immunological tolerance. We will also discuss the functional relationship between IgM-complement and IgM-FcμR pathways in regulating immunity and tolerance. Finally, we will discuss the potential involvement of FcμR in human diseases.
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Affiliation(s)
- Jun Liu
- Department of Immunology, School of Basic Medical Sciences, Fudan University, Shanghai, China
| | - Ying Wang
- Department of Immunology, School of Basic Medical Sciences, Fudan University, Shanghai, China
| | - Ermeng Xiong
- Department of Immunology, School of Basic Medical Sciences, Fudan University, Shanghai, China
| | - Rongjian Hong
- Department of Immunology, School of Basic Medical Sciences, Fudan University, Shanghai, China
| | - Qing Lu
- Department of Immunology, School of Basic Medical Sciences, Fudan University, Shanghai, China
| | - Hiroshi Ohno
- RIKEN Center for Integrative Medical Sciences, Kanagawa, Japan
| | - Ji-Yang Wang
- Department of Immunology, School of Basic Medical Sciences, Fudan University, Shanghai, China
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10
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Pérez D, Stojanovich L, Naranjo L, Stanisavljevic N, Bogdanovic G, Serrano M, Serrano A. Presence of Immune Complexes of IgG/IgM Bound to B2-glycoprotein I Is Associated With Non-criteria Clinical Manifestations in Patients With Antiphospholipid Syndrome. Front Immunol 2018; 9:2644. [PMID: 30524428 PMCID: PMC6256181 DOI: 10.3389/fimmu.2018.02644] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2018] [Accepted: 10/26/2018] [Indexed: 11/26/2022] Open
Abstract
Background: Antiphospholipid syndrome (APS) is an acquired autoimmune disorder defined by the presence of both clinical (thromboembolic events or pregnancy morbidity) and laboratory (antiphospholipid antibodies, aPL) manifestations. Despite their importance, several clinical manifestations strongly associated with APS such as livedo reticularis (LR), thrombocytopenia, sicca-ophthalmic(sicca), heart, or neurological manifestations are not included in the APS clinical classification criteria. Circulating immune complexes (CIC) formed by Beta-2-glycoprotein I (B2GPI) and aPL (B2-CIC) have been described and their presence has been related with thrombotic events. Methods: Cross-sectional and observational cohort study in APS patients with thrombotic symptomatology. Setting and Participants: Fifty-seven patients from the University Hospital Center Bezanijska Kosa (Belgrade, Serbia) who met the APS classification criteria (35 with primary APS and 22 with APS associated to systemic lupus erythematosus). This study aimed to determine the prevalence of B2-CIC in APS patients and to evaluate their association with clinical manifestations of APS not included in the classification criteria. Results: B2-CIC prevalence in APS patients was 19.3%. The presence of thrombocytopenia (OR:5.7), livedo reticularis (OR:5.6), sicca (OR:12.6), and leukopenia (OR:5.6) was significantly higher in patients with B2-CIC than in the rest of APS patients. C3 and C4 complement factor levels were significantly lower in B2-CIC positive patients, which suggests a greater consumption of complement. Patients with quadruple aPL positivity (triple aPL-positivity plus the presence of B2-CIC) showed a higher prevalence of thrombocytopenia, leucopenia and LR than those with single/double aPL-positivity. No significant differences were found in the frequencies observed in patients with triple-only vs. single/double aPL-positivity. There were no significant differences between patients with primary APS and lupus-associated APS regarding the prevalence of B2-CIC and outcomes. Conclusions: Presence of B2-CIC is strongly associated with several non-criteria clinical manifestations related to APS and to higher complement consumption. More studies are required to better understand the clinical significance of B2-CIC.
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Affiliation(s)
- Dolores Pérez
- Immunology Department, Hospital 12 de Octubre, Madrid, Spain
| | - Ljudmila Stojanovich
- Internal Medicine, "Bezanijska Kosa", University Medical Center, Belgrade, Serbia
| | - Laura Naranjo
- Immunology Department, Hospital 12 de Octubre, Madrid, Spain
| | | | - Gordana Bogdanovic
- Internal Medicine, "Bezanijska Kosa", University Medical Center, Belgrade, Serbia
| | - Manuel Serrano
- Immunology Department, Hospital 12 de Octubre, Madrid, Spain
| | - Antonio Serrano
- Immunology Department, Hospital 12 de Octubre, Madrid, Spain
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