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Ünlü S, Sánchez Navarro BG, Cakan E, Berchtold D, Meleka Hanna R, Vural S, Vural A, Meisel A, Fichtner ML. Exploring the depths of IgG4: insights into autoimmunity and novel treatments. Front Immunol 2024; 15:1346671. [PMID: 38698867 PMCID: PMC11063302 DOI: 10.3389/fimmu.2024.1346671] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2023] [Accepted: 02/29/2024] [Indexed: 05/05/2024] Open
Abstract
IgG4 subclass antibodies represent the rarest subclass of IgG antibodies, comprising only 3-5% of antibodies circulating in the bloodstream. These antibodies possess unique structural features, notably their ability to undergo a process known as fragment-antigen binding (Fab)-arm exchange, wherein they exchange half-molecules with other IgG4 antibodies. Functionally, IgG4 antibodies primarily block and exert immunomodulatory effects, particularly in the context of IgE isotype-mediated hypersensitivity reactions. In the context of disease, IgG4 antibodies are prominently observed in various autoimmune diseases combined under the term IgG4 autoimmune diseases (IgG4-AID). These diseases include myasthenia gravis (MG) with autoantibodies against muscle-specific tyrosine kinase (MuSK), nodo-paranodopathies with autoantibodies against paranodal and nodal proteins, pemphigus vulgaris and foliaceus with antibodies against desmoglein and encephalitis with antibodies against LGI1/CASPR2. Additionally, IgG4 antibodies are a prominent feature in the rare entity of IgG4 related disease (IgG4-RD). Intriguingly, both IgG4-AID and IgG4-RD demonstrate a remarkable responsiveness to anti-CD20-mediated B cell depletion therapy (BCDT), suggesting shared underlying immunopathologies. This review aims to provide a comprehensive exploration of B cells, antibody subclasses, and their general properties before examining the distinctive characteristics of IgG4 subclass antibodies in the context of health, IgG4-AID and IgG4-RD. Furthermore, we will examine potential therapeutic strategies for these conditions, with a special focus on leveraging insights gained from anti-CD20-mediated BCDT. Through this analysis, we aim to enhance our understanding of the pathogenesis of IgG4-mediated diseases and identify promising possibilities for targeted therapeutic intervention.
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Affiliation(s)
- Selen Ünlü
- Koç University Research Center for Translational Medicine (KUTTAM), İstanbul, Türkiye
- Koç University School of Medicine, Istanbul, Türkiye
| | - Blanca G. Sánchez Navarro
- Department of Neurology with Experimental Neurology, Integrated Myasthenia Gravis Center, Neuroscience Clinical Research Center, Charité Universitätsmedizin Berlin, Berlin, Germany
| | - Elif Cakan
- Ragon Institute of Massachusetts General Hospital, Massachusetts Institute of Technology and Harvard University, Cambridge, MA, United States
| | - Daniel Berchtold
- Department of Neurology with Experimental Neurology, Integrated Myasthenia Gravis Center, Neuroscience Clinical Research Center, Charité Universitätsmedizin Berlin, Berlin, Germany
| | - Rafael Meleka Hanna
- Department of Neurology with Experimental Neurology, Integrated Myasthenia Gravis Center, Neuroscience Clinical Research Center, Charité Universitätsmedizin Berlin, Berlin, Germany
| | - Secil Vural
- Koç University Research Center for Translational Medicine (KUTTAM), İstanbul, Türkiye
- Department of Dermatology and Venereology, Koç University School of Medicine, İstanbul, Türkiye
| | - Atay Vural
- Koç University Research Center for Translational Medicine (KUTTAM), İstanbul, Türkiye
- Department of Neurology, Koç University School of Medicine, İstanbul, Türkiye
| | - Andreas Meisel
- Department of Neurology with Experimental Neurology, Integrated Myasthenia Gravis Center, Neuroscience Clinical Research Center, Charité Universitätsmedizin Berlin, Berlin, Germany
| | - Miriam L. Fichtner
- Koç University Research Center for Translational Medicine (KUTTAM), İstanbul, Türkiye
- Department of Neurology with Experimental Neurology, Integrated Myasthenia Gravis Center, Neuroscience Clinical Research Center, Charité Universitätsmedizin Berlin, Berlin, Germany
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He T, Chen K, Li Y, Luo Z, Luo M, Yang H. Clinical Features and Prognostic Analysis of MuSK-Antibody-Positive Myasthenia Gravis versus Double-Seropositive Myasthenia Gravis: A Single-Center Study from Central South China. Neuropsychiatr Dis Treat 2024; 20:725-735. [PMID: 38566882 PMCID: PMC10986406 DOI: 10.2147/ndt.s450651] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/02/2023] [Accepted: 03/13/2024] [Indexed: 04/04/2024] Open
Abstract
Purpose To decipher the discrepancies between muscle-specific kinase antibody-positive myasthenia gravis (MuSK-MG) and double-seropositive myasthenia gravis (DSP-MG), and to determine prognostic factors for minimal manifestation status (MMS) achievement in MG patients with MuSK autoantibodies (MuSK-Ab). Patients and Methods A total of 34 MG patients seropositive for MuSK-Ab were enrolled in this study. The demographic and clinical features were compared between MuSK-MG (n = 28) and DSP-MG (n = 6) patients, and factors affecting MMS induction in all patients with MuSK-Ab were identified using Cox regression analysis. Results Compared to MuSK-MG patients, those with DSP-MG had similar clinical characteristics, except that they had a lower frequency of bulbar muscle involvement at nadir (50% vs 92.9%; P = 0.029) and higher proportions of comorbidities with diabetes mellitus (33.3% vs 0%; P = 0.027) and thymic abnormalities (33.3% vs 0%; P = 0.027). Higher MG Activities of Daily Living (MG-ADL) scores (HR = 0.16, 95% CI: 0.037-0.7, P = 0.015) and axial muscle involvement at nadir (HR = 0.39, 95% CI: 0.16-0.94, P = 0.035) were negative prognostic factors for MMS achievement in patients with MuSK-Ab regardless of acetylcholine receptor antibody (AChR-Ab) positivity. Multivariable Cox regression analysis further established higher MG-ADL scores at the nadir (HR = 0.19, 95% CI: 0.04-0.94; P = 0.042) as an independent risk factor for MMS achievement. Conclusion DSP-MG was comparable to MuSK-MG and could be considered a single entity in our cohort. In all MG patients with MuSK-Ab, a higher MG-ADL score at nadir may herald a lower chance of MMS achievement, with no observed potential effect of AChR-Ab presence.
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Affiliation(s)
- Ting He
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, 410008, People’s Republic of China
| | - Kangzhi Chen
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, 410008, People’s Republic of China
| | - Yi Li
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, 410008, People’s Republic of China
| | - Zhaohui Luo
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, 410008, People’s Republic of China
| | - Mengchuan Luo
- Department of Geriatrics, Xiangya Hospital, Central South University, Changsha, 410008, People’s Republic of China
| | - Huan Yang
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, 410008, People’s Republic of China
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Dziadkowiak E, Baczyńska D, Waliszewska-Prosół M. MuSK Myasthenia Gravis-Potential Pathomechanisms and Treatment Directed against Specific Targets. Cells 2024; 13:556. [PMID: 38534400 DOI: 10.3390/cells13060556] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2024] [Revised: 03/17/2024] [Accepted: 03/19/2024] [Indexed: 03/28/2024] Open
Abstract
Myasthenia gravis (MG) is an autoimmune disease in which autoantibodies target structures within the neuromuscular junction, affecting neuromuscular transmission. Muscle-specific tyrosine kinase receptor-associated MG (MuSK-MG) is a rare, often more severe, subtype of the disease with different pathogenesis and specific clinical features. It is characterized by a more severe clinical course, more frequent complications, and often inadequate response to treatment. Here, we review the current state of knowledge about potential pathomechanisms of the MuSK-MG and their therapeutic implications as well as ongoing research in this field, with reference to key points of immune-mediated processes involved in the background of myasthenia gravis.
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Affiliation(s)
- Edyta Dziadkowiak
- Department of Neurology, Wroclaw Medical University, Borowska 213, 50-556 Wroclaw, Poland
| | - Dagmara Baczyńska
- Department of Molecular and Cellular Biology, Wroclaw Medical University, Borowska 211A, 50-556 Wroclaw, Poland
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4
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Damelang T, Brinkhaus M, van Osch TLJ, Schuurman J, Labrijn AF, Rispens T, Vidarsson G. Impact of structural modifications of IgG antibodies on effector functions. Front Immunol 2024; 14:1304365. [PMID: 38259472 PMCID: PMC10800522 DOI: 10.3389/fimmu.2023.1304365] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2023] [Accepted: 12/11/2023] [Indexed: 01/24/2024] Open
Abstract
Immunoglobulin G (IgG) antibodies are a critical component of the adaptive immune system, binding to and neutralizing pathogens and other foreign substances. Recent advances in molecular antibody biology and structural protein engineering enabled the modification of IgG antibodies to enhance their therapeutic potential. This review summarizes recent progress in both natural and engineered structural modifications of IgG antibodies, including allotypic variation, glycosylation, Fc engineering, and Fc gamma receptor binding optimization. We discuss the functional consequences of these modifications to highlight their potential for therapeutical applications.
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Affiliation(s)
- Timon Damelang
- Sanquin Research, Department of Experimental Immunohematology and Landsteiner Laboratory, Amsterdam, Netherlands
- Sanquin Research, Department of Immunopathology, Amsterdam, Netherlands
- Department of Biomolecular Mass Spectrometry and Proteomics, Utrecht Institute for Pharmaceutical Sciences and Bijvoet Center for Biomolecular Research, Utrecht University, Utrecht, Netherlands
- Department of Antibody Research & Technologies’, Genmab, Utrecht, Netherlands
| | - Maximilian Brinkhaus
- Sanquin Research, Department of Experimental Immunohematology and Landsteiner Laboratory, Amsterdam, Netherlands
- Department of Biomolecular Mass Spectrometry and Proteomics, Utrecht Institute for Pharmaceutical Sciences and Bijvoet Center for Biomolecular Research, Utrecht University, Utrecht, Netherlands
| | - Thijs L. J. van Osch
- Sanquin Research, Department of Experimental Immunohematology and Landsteiner Laboratory, Amsterdam, Netherlands
- Department of Biomolecular Mass Spectrometry and Proteomics, Utrecht Institute for Pharmaceutical Sciences and Bijvoet Center for Biomolecular Research, Utrecht University, Utrecht, Netherlands
| | - Janine Schuurman
- Department of Antibody Research & Technologies’, Genmab, Utrecht, Netherlands
| | - Aran F. Labrijn
- Department of Antibody Research & Technologies’, Genmab, Utrecht, Netherlands
| | - Theo Rispens
- Sanquin Research, Department of Immunopathology, Amsterdam, Netherlands
| | - Gestur Vidarsson
- Sanquin Research, Department of Experimental Immunohematology and Landsteiner Laboratory, Amsterdam, Netherlands
- Department of Biomolecular Mass Spectrometry and Proteomics, Utrecht Institute for Pharmaceutical Sciences and Bijvoet Center for Biomolecular Research, Utrecht University, Utrecht, Netherlands
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Jaime D, Fish LA, Madigan LA, Xi C, Piccoli G, Ewing MD, Blaauw B, Fallon JR. The MuSK-BMP pathway maintains myofiber size in slow muscle through regulation of Akt-mTOR signaling. Skelet Muscle 2024; 14:1. [PMID: 38172960 PMCID: PMC10763067 DOI: 10.1186/s13395-023-00329-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2023] [Accepted: 10/19/2023] [Indexed: 01/05/2024] Open
Abstract
Myofiber size regulation is critical in health, disease, and aging. MuSK (muscle-specific kinase) is a BMP (bone morphogenetic protein) co-receptor that promotes and shapes BMP signaling. MuSK is expressed at all neuromuscular junctions and is also present extrasynaptically in the mouse soleus, whose predominantly oxidative fiber composition is akin to that of human muscle. To investigate the role of the MuSK-BMP pathway in vivo, we generated mice lacking the BMP-binding MuSK Ig3 domain. These ∆Ig3-MuSK mice are viable and fertile with innervation levels comparable to wild type. In 3-month-old mice, myofibers are smaller in the slow soleus, but not in the fast tibialis anterior (TA). Transcriptomic analysis revealed soleus-selective decreases in RNA metabolism and protein synthesis pathways as well as dysregulation of IGF1-Akt-mTOR pathway components. Biochemical analysis showed that Akt-mTOR signaling is reduced in soleus but not TA. We propose that the MuSK-BMP pathway acts extrasynaptically to maintain myofiber size in slow muscle by promoting protein synthetic pathways including IGF1-Akt-mTOR signaling. These results reveal a novel mechanism for regulating myofiber size in slow muscle and introduce the MuSK-BMP pathway as a target for promoting muscle growth and combatting atrophy.
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Grants
- R41 AG073144 NIA NIH HHS
- T32 MH020068 NIMH NIH HHS
- U01 NS064295, R41 AG073144, R21 NS112743, R21 AG073743, P30 GM103410, P30 RR031153, P20 RR018728, S10 RR02763, R25GM083270, 2T32AG041688, and T32 MH20068 NIH HHS
- P30 GM103410 NIGMS NIH HHS
- T32 AG041688 NIA NIH HHS
- P30 RR031153 NCRR NIH HHS
- U01 NS064295 NINDS NIH HHS
- R21 NS112743 NINDS NIH HHS
- P20 RR018728 NCRR NIH HHS
- R21 AG073743 NIA NIH HHS
- R25 GM083270 NIGMS NIH HHS
- National Institutes of Health
- Carney Institute for Brain Sciences
- ALS Finding a Cure
- AFM-Téléthon
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Affiliation(s)
- Diego Jaime
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, RI, USA
| | - Lauren A Fish
- Department of Neuroscience, Brown University, Providence, RI, 02912, USA
| | - Laura A Madigan
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, RI, USA
| | - Chengjie Xi
- Department of Neuroscience, Brown University, Providence, RI, 02912, USA
| | - Giorgia Piccoli
- Veneto Institute of Molecular Medicine (VIMM), Padua, Italy
- Department of Biomedical Sciences, University of Padua, Padua, Italy
| | - Madison D Ewing
- Department of Neuroscience, Brown University, Providence, RI, 02912, USA
| | - Bert Blaauw
- Veneto Institute of Molecular Medicine (VIMM), Padua, Italy
- Department of Biomedical Sciences, University of Padua, Padua, Italy
| | - Justin R Fallon
- Department of Neuroscience, Brown University, Providence, RI, 02912, USA.
- Carney Institute for Neuroscience, Brown University, Providence, RI, USA.
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Tannemaat MR, Huijbers MG, Verschuuren JJGM. Myasthenia gravis-Pathophysiology, diagnosis, and treatment. HANDBOOK OF CLINICAL NEUROLOGY 2024; 200:283-305. [PMID: 38494283 DOI: 10.1016/b978-0-12-823912-4.00026-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/19/2024]
Abstract
Myasthenia gravis (MG) is an autoimmune disease characterized by dysfunction of the neuromuscular junction resulting in skeletal muscle weakness. It is equally prevalent in males and females, but debuts at a younger age in females and at an older age in males. Ptosis, diplopia, facial bulbar weakness, and limb weakness are the most common symptoms. MG can be classified based on the presence of serum autoantibodies. Acetylcholine receptor (AChR) antibodies are found in 80%-85% of patients, muscle-specific kinase (MuSK) antibodies in 5%-8%, and <1% may have low-density lipoprotein receptor-related protein 4 (Lrp4) antibodies. Approximately 10% of patients are seronegative for antibodies binding the known disease-related antigens. In patients with AChR MG, 10%-20% have a thymoma, which is usually detected at the onset of the disease. Important differences between clinical presentation, treatment responsiveness, and disease mechanisms have been observed between these different serologic MG classes. Besides the typical clinical features and serologic testing, the diagnosis can be established with additional tests, including repetitive nerve stimulation, single fiber EMG, and the ice pack test. Treatment options for MG consist of symptomatic treatment (such as pyridostigmine), immunosuppressive treatment, or thymectomy. Despite the treatment with symptomatic drugs, steroid-sparing immunosuppressants, intravenous immunoglobulins, plasmapheresis, and thymectomy, a large proportion of patients remain chronically dependent on corticosteroids (CS). In the past decade, the number of treatment options for MG has considerably increased. Advances in the understanding of the pathophysiology have led to new treatment options targeting B or T cells, the complement cascade, the neonatal Fc receptor or cytokines. In the future, these new treatments are likely to reduce the chronic use of CS, diminish side effects, and decrease the number of patients with refractory disease.
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Affiliation(s)
- Martijn R Tannemaat
- Department of Neurology, Leiden University Medical Center, Leiden, The Netherlands
| | - Maartje G Huijbers
- Department of Neurology, Leiden University Medical Center, Leiden, The Netherlands; Department of Human Genetics, Leiden University Medical Center, Leiden, The Netherlands
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7
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Paardekooper LM, Fillié-Grijpma YE, van der Sluijs-Gelling AJ, Zlei M, van Doorn R, Vermeer MH, Paunovic M, Titulaer MJ, van der Maarel SM, van Dongen JJM, Verschuuren JJ, Huijbers MG. Autoantibody subclass predominance is not driven by aberrant class switching or impaired B cell development. Clin Immunol 2023; 257:109817. [PMID: 37925120 DOI: 10.1016/j.clim.2023.109817] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2023] [Revised: 09/25/2023] [Accepted: 10/25/2023] [Indexed: 11/06/2023]
Abstract
A subset of autoimmune diseases is characterized by predominant pathogenic IgG4 autoantibodies (IgG4-AID). Why IgG4 predominates in these disorders is unknown. We hypothesized that dysregulated B cell maturation or aberrant class switching causes overrepresentation of IgG4+ B cells and plasma cells. Therefore, we compared the B cell compartment of patients from four different IgG4-AID with two IgG1-3-AID and healthy donors, using flow cytometry. Relative subset abundance at all maturation stages was normal, except for a, possibly treatment-related, reduction in immature and naïve CD5+ cells. IgG4+ B cell and plasma cell numbers were normal in IgG4-AID patients, however they had a (sub)class-independent 8-fold increase in circulating CD20-CD138+ cells. No autoreactivity was found in this subset. These results argue against aberrant B cell development and rather suggest the autoantibody subclass predominance to be antigen-driven. The similarities between IgG4-AID suggest that, despite displaying variable clinical phenotypes, they share a similar underlying immune profile.
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Affiliation(s)
| | | | | | - Mihaela Zlei
- Department of Immunology, Leiden University Medical Center, Leiden, The Netherlands
| | - Remco van Doorn
- Department of Dermatology, Leiden University Medical Center, Leiden, The Netherlands
| | - Maarten H Vermeer
- Department of Dermatology, Leiden University Medical Center, Leiden, The Netherlands
| | - Manuela Paunovic
- Department of Neurology, Erasmus University Medical Center, Rotterdam, The Netherlands
| | - Maarten J Titulaer
- Department of Neurology, Erasmus University Medical Center, Rotterdam, The Netherlands
| | | | - Jacques J M van Dongen
- Department of Immunology, Leiden University Medical Center, Leiden, The Netherlands; Centro de Investigación del Cáncer-Instituto de Biología Molecular y Celular del Cáncer (CIC-IBMCC, USAL-CSIC-FICUS) and Department of Medicine, University of Salamanca, Salamanca, Spain
| | - Jan J Verschuuren
- Department of Neurology, Leiden University Medical Center, Leiden, The Netherlands
| | - Maartje G Huijbers
- Department of Human Genetics, Leiden University Medical Center, Leiden, The Netherlands; Department of Neurology, Leiden University Medical Center, Leiden, The Netherlands.
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Cao M, Liu WW, Maxwell S, Huda S, Webster R, Evoli A, Beeson D, Cossins JA, Vincent A. IgG1-3 MuSK Antibodies Inhibit AChR Cluster Formation, Restored by SHP2 Inhibitor, Despite Normal MuSK, DOK7, or AChR Subunit Phosphorylation. NEUROLOGY(R) NEUROIMMUNOLOGY & NEUROINFLAMMATION 2023; 10:e200147. [PMID: 37582613 PMCID: PMC10427144 DOI: 10.1212/nxi.0000000000200147] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2023] [Accepted: 06/07/2023] [Indexed: 08/17/2023]
Abstract
BACKGROUND AND OBJECTIVES Up to 50% of patients with myasthenia gravis (MG) without acetylcholine receptor antibodies (AChR-Abs) have antibodies to muscle-specific kinase (MuSK). Most MuSK antibodies (MuSK-Abs) are IgG4 and inhibit agrin-induced MuSK phosphorylation, leading to impaired clustering of AChRs at the developing or mature neuromuscular junction. However, IgG1-3 MuSK-Abs also exist in MuSK-MG patients, and their potential mechanisms have not been explored fully. METHODS C2C12 myotubes were exposed to MuSK-MG plasma IgG1-3 or IgG4, with or without purified agrin. MuSK, Downstream of Kinase 7 (DOK7), and βAChR were immunoprecipitated and their phosphorylation levels identified by immunoblotting. Agrin and agrin-independent AChR clusters were measured by immunofluorescence and AChR numbers by binding of 125I-α-bungarotoxin. Transcriptomic analysis was performed on treated myotubes. RESULTS IgG1-3 MuSK-Abs impaired AChR clustering without inhibiting agrin-induced MuSK phosphorylation. Moreover, the well-established pathway initiated by MuSK through DOK7, resulting in βAChR phosphorylation, was not impaired by MuSK-IgG1-3 and was agrin-independent. Nevertheless, the AChR clusters did not form, and both the number of AChR microclusters that precede full cluster formation and the myotube surface AChRs were reduced. Transcriptomic analysis did not throw light on the pathways involved. However, the SHP2 inhibitor, NSC-87877, increased the number of microclusters and led to fully formed AChR clusters. DISCUSSION MuSK-IgG1-3 is pathogenic but seems to act through a noncanonical pathway. Further studies should throw light on the mechanisms involved at the neuromuscular junction.
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Affiliation(s)
- Michelangelo Cao
- From the Nuffield Department of Clinical Neurosciences (M.C., W.W.L., S.M., R.W., D.B., J.A.C., A.V.), University of Oxford; Norfolk and Norwich University Hospital (M.C.); The Walton Centre NHS Foundation Trust (S.H.), Liverpool, United Kingdom; and Department of Neuroscience (A.E.), Catholic University, Rome, Italy
| | - Wei-Wei Liu
- From the Nuffield Department of Clinical Neurosciences (M.C., W.W.L., S.M., R.W., D.B., J.A.C., A.V.), University of Oxford; Norfolk and Norwich University Hospital (M.C.); The Walton Centre NHS Foundation Trust (S.H.), Liverpool, United Kingdom; and Department of Neuroscience (A.E.), Catholic University, Rome, Italy
| | - Susan Maxwell
- From the Nuffield Department of Clinical Neurosciences (M.C., W.W.L., S.M., R.W., D.B., J.A.C., A.V.), University of Oxford; Norfolk and Norwich University Hospital (M.C.); The Walton Centre NHS Foundation Trust (S.H.), Liverpool, United Kingdom; and Department of Neuroscience (A.E.), Catholic University, Rome, Italy
| | - Saif Huda
- From the Nuffield Department of Clinical Neurosciences (M.C., W.W.L., S.M., R.W., D.B., J.A.C., A.V.), University of Oxford; Norfolk and Norwich University Hospital (M.C.); The Walton Centre NHS Foundation Trust (S.H.), Liverpool, United Kingdom; and Department of Neuroscience (A.E.), Catholic University, Rome, Italy
| | - Richard Webster
- From the Nuffield Department of Clinical Neurosciences (M.C., W.W.L., S.M., R.W., D.B., J.A.C., A.V.), University of Oxford; Norfolk and Norwich University Hospital (M.C.); The Walton Centre NHS Foundation Trust (S.H.), Liverpool, United Kingdom; and Department of Neuroscience (A.E.), Catholic University, Rome, Italy
| | - Amelia Evoli
- From the Nuffield Department of Clinical Neurosciences (M.C., W.W.L., S.M., R.W., D.B., J.A.C., A.V.), University of Oxford; Norfolk and Norwich University Hospital (M.C.); The Walton Centre NHS Foundation Trust (S.H.), Liverpool, United Kingdom; and Department of Neuroscience (A.E.), Catholic University, Rome, Italy
| | - David Beeson
- From the Nuffield Department of Clinical Neurosciences (M.C., W.W.L., S.M., R.W., D.B., J.A.C., A.V.), University of Oxford; Norfolk and Norwich University Hospital (M.C.); The Walton Centre NHS Foundation Trust (S.H.), Liverpool, United Kingdom; and Department of Neuroscience (A.E.), Catholic University, Rome, Italy
| | - Judith A Cossins
- From the Nuffield Department of Clinical Neurosciences (M.C., W.W.L., S.M., R.W., D.B., J.A.C., A.V.), University of Oxford; Norfolk and Norwich University Hospital (M.C.); The Walton Centre NHS Foundation Trust (S.H.), Liverpool, United Kingdom; and Department of Neuroscience (A.E.), Catholic University, Rome, Italy
| | - Angela Vincent
- From the Nuffield Department of Clinical Neurosciences (M.C., W.W.L., S.M., R.W., D.B., J.A.C., A.V.), University of Oxford; Norfolk and Norwich University Hospital (M.C.); The Walton Centre NHS Foundation Trust (S.H.), Liverpool, United Kingdom; and Department of Neuroscience (A.E.), Catholic University, Rome, Italy.
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Huang EJC, Wu MH, Wang TJ, Huang TJ, Li YR, Lee CY. Myasthenia Gravis: Novel Findings and Perspectives on Traditional to Regenerative Therapeutic Interventions. Aging Dis 2023; 14:1070-1092. [PMID: 37163445 PMCID: PMC10389825 DOI: 10.14336/ad.2022.1215] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2022] [Accepted: 12/15/2022] [Indexed: 05/12/2023] Open
Abstract
The prevalence of myasthenia gravis (MG), an autoimmune disorder, is increasing among all subsets of the population leading to an elevated economic and social burden. The pathogenesis of MG is characterized by the synthesis of autoantibodies against the acetylcholine receptor (AChR), low-density lipoprotein receptor-related protein 4 (LRP4), or muscle-specific kinase at the neuromuscular junction, thereby leading to muscular weakness and fatigue. Based on clinical and laboratory examinations, the research is focused on distinguishing MG from other autoimmune, genetic diseases of neuromuscular transmission. Technological advancements in machine learning, a subset of artificial intelligence (AI) have been assistive in accurate diagnosis and management. Besides, addressing the clinical needs of MG patients is critical to improving quality of life (QoL) and satisfaction. Lifestyle changes including physical exercise and traditional Chinese medicine/herbs have also been shown to exert an ameliorative impact on MG progression. To achieve enhanced therapeutic efficacy, cholinesterase inhibitors, immunosuppressive drugs, and steroids in addition to plasma exchange therapy are widely recommended. Under surgical intervention, thymectomy is the only feasible alternative to removing thymoma to overcome thymoma-associated MG. Although these conventional and current therapeutic approaches are effective, the associated adverse events and surgical complexity limit their wide application. Moreover, Restivo et al. also, to increase survival and QoL, further recent developments revealed that antibody, gene, and regenerative therapies (such as stem cells and exosomes) are currently being investigated as a safer and more efficacious alternative. Considering these above-mentioned points, we have comprehensively reviewed the recent advances in pathological etiologies of MG including COVID-19, and its therapeutic management.
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Affiliation(s)
- Evelyn Jou-Chen Huang
- Department of Ophthalmology, Taipei Medical University Hospital, Taipei, Taiwan.
- Department of Ophthalmology, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan.
| | - Meng-Huang Wu
- Department of Orthopedics, Taipei Medical University Hospital, Taipei, Taiwan.
- Department of Orthopaedics, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan.
| | - Tsung-Jen Wang
- Department of Ophthalmology, Taipei Medical University Hospital, Taipei, Taiwan.
- Department of Ophthalmology, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan.
| | - Tsung-Jen Huang
- Department of Orthopedics, Taipei Medical University Hospital, Taipei, Taiwan.
- Department of Orthopaedics, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan.
| | - Yan-Rong Li
- Division of Endocrinology and Metabolism, Department of Internal Medicine, Linkou Chang Gung Memorial Hospital and College of Medicine, Chang Gung University, Taoyuan, Taiwan.
| | - Ching-Yu Lee
- Department of Orthopedics, Taipei Medical University Hospital, Taipei, Taiwan.
- Department of Orthopaedics, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan.
- International PhD Program for Cell Therapy and Regeneration Medicine, College of Medicine, Taipei Medical University, Taipei 11031, Taiwan.
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10
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Vakrakou AG, Karachaliou E, Chroni E, Zouvelou V, Tzanetakos D, Salakou S, Papadopoulou M, Tzartos S, Voumvourakis K, Kilidireas C, Giannopoulos S, Tsivgoulis G, Tzartos J. Immunotherapies in MuSK-positive Myasthenia Gravis; an IgG4 antibody-mediated disease. Front Immunol 2023; 14:1212757. [PMID: 37564637 PMCID: PMC10410455 DOI: 10.3389/fimmu.2023.1212757] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2023] [Accepted: 07/05/2023] [Indexed: 08/12/2023] Open
Abstract
Muscle-specific kinase (MuSK) Myasthenia Gravis (MG) represents a prototypical antibody-mediated disease characterized by predominantly focal muscle weakness (neck, facial, and bulbar muscles) and fatigability. The pathogenic antibodies mostly belong to the immunoglobulin subclass (Ig)G4, a feature which attributes them their specific properties and pathogenic profile. On the other hand, acetylcholine receptor (AChR) MG, the most prevalent form of MG, is characterized by immunoglobulin (Ig)G1 and IgG3 antibodies to the AChR. IgG4 class autoantibodies are impotent to fix complement and only weakly bind Fc-receptors expressed on immune cells and exert their pathogenicity via interfering with the interaction between their targets and binding partners (e.g. between MuSK and LRP4). Cardinal differences between AChR and MuSK-MG are the thymus involvement (not prominent in MuSK-MG), the distinct HLA alleles, and core immunopathological patterns of pathology in neuromuscular junction, structure, and function. In MuSK-MG, classical treatment options are usually less effective (e.g. IVIG) with the need for prolonged and high doses of steroids difficult to be tapered to control symptoms. Exceptional clinical response to plasmapheresis and rituximab has been particularly observed in these patients. Reduction of antibody titers follows the clinical efficacy of anti-CD20 therapies, a feature implying the role of short-lived plasma cells (SLPB) in autoantibody production. Novel therapeutic monoclonal against B cells at different stages of their maturation (like plasmablasts), or against molecules involved in B cell activation, represent promising therapeutic targets. A revolution in autoantibody-mediated diseases is pharmacological interference with the neonatal Fc receptor, leading to a rapid reduction of circulating IgGs (including autoantibodies), an approach already suitable for AChR-MG and promising for MuSK-MG. New precision medicine approaches involve Chimeric autoantibody receptor T (CAAR-T) cells that are engineered to target antigen-specific B cells in MuSK-MG and represent a milestone in the development of targeted immunotherapies. This review aims to provide a detailed update on the pathomechanisms involved in MuSK-MG (cellular and humoral aberrations), fostering the understanding of the latest indications regarding the efficacy of different treatment strategies.
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Affiliation(s)
- Aigli G. Vakrakou
- First Department of Neurology, Medical School, National and Kapodistrian University of Athens, Athens, Greece
| | - Eleni Karachaliou
- Second Department of Neurology, Attikon University Hospital, National and Kapodistrian University of Athens, Athens, Greece
| | - Elisabeth Chroni
- Department of Neurology, School of Medicine, University of Patras, Patras, Greece
| | - Vasiliki Zouvelou
- First Department of Neurology, Medical School, National and Kapodistrian University of Athens, Athens, Greece
| | - Dimitrios Tzanetakos
- Second Department of Neurology, Attikon University Hospital, National and Kapodistrian University of Athens, Athens, Greece
| | - Stavroula Salakou
- Second Department of Neurology, Attikon University Hospital, National and Kapodistrian University of Athens, Athens, Greece
| | - Marianna Papadopoulou
- Second Department of Neurology, Attikon University Hospital, National and Kapodistrian University of Athens, Athens, Greece
- Department of Physiotherapy, University of West Attica, Athens, Greece
| | - Socrates Tzartos
- Tzartos NeuroDiagnostics, Athens, Greece
- Department of Neurobiology, Hellenic Pasteur Institute, Athens, Greece
- Department of Pharmacy, University of Patras, Patras, Greece
| | - Konstantinos Voumvourakis
- Second Department of Neurology, Attikon University Hospital, National and Kapodistrian University of Athens, Athens, Greece
| | - Constantinos Kilidireas
- First Department of Neurology, Medical School, National and Kapodistrian University of Athens, Athens, Greece
- Department of Neurology, Henry Dunant Hospital Center, Athens, Greece
| | - Sotirios Giannopoulos
- Second Department of Neurology, Attikon University Hospital, National and Kapodistrian University of Athens, Athens, Greece
| | - Georgios Tsivgoulis
- Second Department of Neurology, Attikon University Hospital, National and Kapodistrian University of Athens, Athens, Greece
- Department of Neurology, The University of Tennessee Health Science Center, Memphis, TN, United States
| | - John Tzartos
- Second Department of Neurology, Attikon University Hospital, National and Kapodistrian University of Athens, Athens, Greece
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11
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Lim JL, Augustinus R, Plomp JJ, Roya-Kouchaki K, Vergoossen DLE, Fillié-Grijpma Y, Struijk J, Thomas R, Salvatori D, Steyaert C, Blanchetot C, Vanhauwaert R, Silence K, van der Maarel SM, Verschuuren JJ, Huijbers MG. Development and characterization of agonistic antibodies targeting the Ig-like 1 domain of MuSK. Sci Rep 2023; 13:7478. [PMID: 37156800 PMCID: PMC10167245 DOI: 10.1038/s41598-023-32641-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2023] [Accepted: 03/30/2023] [Indexed: 05/10/2023] Open
Abstract
Muscle-specific kinase (MuSK) is crucial for acetylcholine receptor (AChR) clustering and thereby neuromuscular junction (NMJ) function. NMJ dysfunction is a hallmark of several neuromuscular diseases, including MuSK myasthenia gravis. Aiming to restore NMJ function, we generated several agonist monoclonal antibodies targeting the MuSK Ig-like 1 domain. These activated MuSK and induced AChR clustering in cultured myotubes. The most potent agonists partially rescued myasthenic effects of MuSK myasthenia gravis patient IgG autoantibodies in vitro. In an IgG4 passive transfer MuSK myasthenia model in NOD/SCID mice, MuSK agonists caused accelerated weight loss and no rescue of myasthenic features. The MuSK Ig-like 1 domain agonists unexpectedly caused sudden death in a large proportion of male C57BL/6 mice (but not female or NOD/SCID mice), likely caused by a urologic syndrome. In conclusion, these agonists rescued pathogenic effects in myasthenia models in vitro, but not in vivo. The sudden death in male mice of one of the tested mouse strains revealed an unexpected and unexplained role for MuSK outside skeletal muscle, thereby hampering further (pre-) clinical development of these clones. Future research should investigate whether other Ig-like 1 domain MuSK antibodies, binding different epitopes, do hold a safe therapeutic promise.
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Affiliation(s)
- Jamie L Lim
- Department of Human Genetics, Leiden University Medical Center, Einthovenweg 20, 2300 RC, Leiden, The Netherlands
| | - Roy Augustinus
- Department of Human Genetics, Leiden University Medical Center, Einthovenweg 20, 2300 RC, Leiden, The Netherlands
| | - Jaap J Plomp
- Department of Neurology, Leiden University Medical Center, Leiden, The Netherlands
| | - Kasra Roya-Kouchaki
- Department of Human Genetics, Leiden University Medical Center, Einthovenweg 20, 2300 RC, Leiden, The Netherlands
| | - Dana L E Vergoossen
- Department of Human Genetics, Leiden University Medical Center, Einthovenweg 20, 2300 RC, Leiden, The Netherlands
| | - Yvonne Fillié-Grijpma
- Department of Human Genetics, Leiden University Medical Center, Einthovenweg 20, 2300 RC, Leiden, The Netherlands
| | - Josephine Struijk
- Department of Human Genetics, Leiden University Medical Center, Einthovenweg 20, 2300 RC, Leiden, The Netherlands
| | - Rachel Thomas
- Department PDC-Pathologie, Leiden University Medical Center, Leiden, The Netherlands
| | - Daniela Salvatori
- Veterinary Faculty, Department Clinical Sciences, Universiteit Utrecht, Utrecht, The Netherlands
| | | | | | | | | | - Silvère M van der Maarel
- Department of Human Genetics, Leiden University Medical Center, Einthovenweg 20, 2300 RC, Leiden, The Netherlands
| | - Jan J Verschuuren
- Department of Neurology, Leiden University Medical Center, Leiden, The Netherlands
| | - Maartje G Huijbers
- Department of Human Genetics, Leiden University Medical Center, Einthovenweg 20, 2300 RC, Leiden, The Netherlands.
- Department of Neurology, Leiden University Medical Center, Leiden, The Netherlands.
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12
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Prömer J, Barresi C, Herbst R. From phosphorylation to phenotype - Recent key findings on kinase regulation, downstream signaling and disease surrounding the receptor tyrosine kinase MuSK. Cell Signal 2023; 104:110584. [PMID: 36608736 DOI: 10.1016/j.cellsig.2022.110584] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2022] [Revised: 12/16/2022] [Accepted: 12/31/2022] [Indexed: 01/04/2023]
Abstract
Muscle-specific kinase (MuSK) is the key regulator of neuromuscular junction development. MuSK acts via several distinct pathways and is responsible for pre- and postsynaptic differentiation. MuSK is unique among receptor tyrosine kinases as activation and signaling are particularly tightly regulated. Initiation of kinase activity requires Agrin, a heparan sulphate proteoglycan derived from motor neurons, the low-density lipoprotein receptor-related protein-4 (Lrp4) and the intracellular adaptor protein Dok-7. There is a great knowledge gap between MuSK activation and downstream signaling. Recent studies using omics techniques have addressed this knowledge gap, thereby greatly contributing to a better understanding of MuSK signaling. Impaired MuSK signaling causes severe muscle weakness as described in congenital myasthenic syndromes or myasthenia gravis but the underlying pathophysiology is often unclear. This review focuses on recent advances in deciphering MuSK activation and downstream signaling. We further highlight latest break-throughs in understanding and treatment of MuSK-related disorders and discuss the role of MuSK in non-muscle tissue.
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Affiliation(s)
- Jakob Prömer
- Center for Pathophysiology, Infectiology and Immunology, Medical University of Vienna, Vienna, Austria
| | - Cinzia Barresi
- Center for Pathophysiology, Infectiology and Immunology, Medical University of Vienna, Vienna, Austria
| | - Ruth Herbst
- Center for Pathophysiology, Infectiology and Immunology, Medical University of Vienna, Vienna, Austria.
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13
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Abstract
Repeated doses of mRNA vaccines for COVID-19 result in increased proportions of anti-spike antibodies of the IgG4 subclass, which are known to neutralize well and to form mixed immune complexes with IgG1 but, in a pure form, might be less effective than IgG1 or IgG3 antibodies in facilitating opsonization by phagocytes, complement fixation, and NK cell-dependent elimination of infected cells (see related Research Article by Irrgang et al.).
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Affiliation(s)
- Shiv Pillai
- Ragon Institute of MGH, MIT and Harvard, Cambridge, MA, USA
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14
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Taieb G, Jentzer A, Vegezzi E, Lleixà C, Illa I, Querol L, Devaux JJ. Effect of monovalency on anti-contactin-1 IgG4. Front Immunol 2023; 14:1021513. [PMID: 36999029 PMCID: PMC10045471 DOI: 10.3389/fimmu.2023.1021513] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2022] [Accepted: 03/02/2023] [Indexed: 03/15/2023] Open
Abstract
IntroductionAutoimmune nodopathies (AN) have been diagnosed in a subset of patients fulfilling criteria for chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) who display no or poor response to intravenous immunoglobulins. Biomarkers of AN are autoantibodies, mainly IgG4, directed against the ternary paranodal complex composed by neurofascin-155, contactin-1 (CNTN1), and Contactin-associated-protein-1 (CASPR1) or against the nodal isoforms of neurofascin. IgG4 can undergo a Fab-arm exchange (FAE) which results in functionally monovalent antibody. This phenomenon differentially affects the pathogenicity of IgG4 depending on the target of autoantibodies. Here, we have evaluated this issue by examining the impact of valency on anti-CNTN1 IgG4 which induces paranodal destruction through a function blocking activity.MethodsSera were obtained from 20 patients with AN associated with anti-CNTN1 antibodies. The proportion of monospecific/bispecific anti-CNTN1 antibodies was estimated in each patient by ELISA by examining the ability of serum antibodies to cross-link untagged CNTN1 with biotinylated CNTN1. To determine the impact of monovalency, anti-CNTN1 IgG4 were enzymatically digested into monovalent Fab and tested in vitro on cell aggregation assay. Also, intraneural injections were performed to determine whether monovalent Fab and native IgG4 may penetrate paranode, and antibody infiltration was monitored 1- and 3-days post injection.Results and discussionWe found that the percentage of monospecific antibodies were lower than 5% in 14 out of 20 patients (70%), suggesting that IgG4 have undergone extensive FAE in situ. The levels of monospecific antibodies correlated with the titers of anti-CNTN1 antibodies. However, no correlation was found with clinical severity, and patients with low or high percentage of monospecific antibodies similarly showed a severe phenotype. Native anti-CNTN1 IgG4 were shown to inhibit the interaction between cells expressing CNTN1/CASPR1 and cells expressing neurofascin-155 using an in vitro aggregation assay. Similarly, monovalent Fab significantly inhibited the interaction between CNTN1/CASPR1 and neurofascin-155. Intraneural injections of Fab and native anti-CNTN1 IgG4 indicated that both mono- and bivalent anti-CNTN1 IgG4 potently penetrated the paranodal regions and completely invaded this region by day 3. Altogether, these data indicate anti-CNTN1 IgG4 are mostly bispecific in patients, and that functionally monovalent anti-CNTN1 antibodies have the pathogenic potency to alter paranode.
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Affiliation(s)
- Guillaume Taieb
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, INSERM, Montpellier, France
- Department of Neurology, CHU Montpellier, Hôpital Gui de Chauliac, Montpellier, France
| | - Alexandre Jentzer
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, INSERM, Montpellier, France
- Department of Immunology, CHU Montpellier, Hôpital Saint-Eloi, Montpellier, France
| | - Elisa Vegezzi
- Department of Brain and Behavioral Sciences, University of Pavia, Pavia, Italy
| | - Cinta Lleixà
- Neuromuscular Diseases Unit, Hospital de la Santa Creu i Sant Pau, Universitat Autónoma de Barcelona, Barcelona, Spain
| | - Isabel Illa
- Neuromuscular Diseases Unit, Hospital de la Santa Creu i Sant Pau, Universitat Autónoma de Barcelona, Barcelona, Spain
| | - Luis Querol
- Neuromuscular Diseases Unit, Hospital de la Santa Creu i Sant Pau, Universitat Autónoma de Barcelona, Barcelona, Spain
| | - Jérôme J. Devaux
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, INSERM, Montpellier, France
- *Correspondence: Jérôme J. Devaux,
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15
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Behbehani R. Ocular Myasthenia Gravis: A Current Overview. Eye Brain 2023; 15:1-13. [PMID: 36778719 PMCID: PMC9911903 DOI: 10.2147/eb.s389629] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2022] [Accepted: 01/24/2023] [Indexed: 02/05/2023] Open
Abstract
Ocular myasthenia gravis (OMG) is a neuromuscular disease characterized by autoantibody production against post-synaptic proteins in the neuromuscular junction. The pathophysiological auto-immune mechanisms of myasthenia are diverse, and this is governed primarily by the type of autoantibody production. The diagnosis of OMG relies mainly on clinical assessment, the use of serological antibody assays for acetylcholine receptors (AchR), muscle-specific tyrosine kinase (MusK), and low-density lipoprotein 4 (LPR4). Other autoantibodies against post-synaptic proteins, such as cortactin and agrin, have been detected; however, their diagnostic value and pathogenic effect are not yet clearly defined. Clinical tests such as the ice test and electrophysiologic tests, particularly single-fiber electromyography, have a valuable role in diagnosis. The treatment of OMG is primarily through cholinesterase inhibitors (pyridostigmine), and steroids are frequently required in cases of ophthalmoplegia. Other immunosuppressive therapies include antimetabolites (azathioprine, mycophenolate mofetil, methotrexate) and biological agents such as B-cell depleting agents (Rituximab) and complement inhibitors (eculizumab). Evidence is scarce on the effect of immunosuppressive therapy on altering the natural course of OMG. Clinicians must be vigilant of a myasthenic syndrome in patients using immune-check inhibitors. Reliable and consistent biomarkers are required to assess disease severity and response to therapy to optimize the management of OMG. The purpose of this review is to summarize the current trends and the latest developments in diagnosing and treating OMG.
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Affiliation(s)
- Raed Behbehani
- Neuroophthalmology Unit, Ibn Sina Hospital, Kuwait City, Kuwait,Correspondence: Raed Behbehani, Ibn Sina Hospital, P.O Box 1180, Tel +965 2224 2999, Fax +965 2249 2406, Email
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16
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Fichtner ML, Hoehn KB, Ford EE, Mane-Damas M, Oh S, Waters P, Payne AS, Smith ML, Watson CT, Losen M, Martinez-Martinez P, Nowak RJ, Kleinstein SH, O'Connor KC. Reemergence of pathogenic, autoantibody-producing B cell clones in myasthenia gravis following B cell depletion therapy. Acta Neuropathol Commun 2022; 10:154. [PMID: 36307868 PMCID: PMC9617453 DOI: 10.1186/s40478-022-01454-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2022] [Accepted: 09/30/2022] [Indexed: 11/12/2022] Open
Abstract
Myasthenia gravis (MG) is an autoantibody-mediated autoimmune disorder of the neuromuscular junction. A small subset of patients (<10%) with MG, have autoantibodies targeting muscle-specific tyrosine kinase (MuSK). MuSK MG patients respond well to CD20-mediated B cell depletion therapy (BCDT); most achieve complete stable remission. However, relapse often occurs. To further understand the immunomechanisms underlying relapse, we studied autoantibody-producing B cells over the course of BCDT. We developed a fluorescently labeled antigen to enrich for MuSK-specific B cells, which was validated with a novel Nalm6 cell line engineered to express a human MuSK-specific B cell receptor. B cells (≅ 2.6 million) from 12 different samples collected from nine MuSK MG patients were screened for MuSK specificity. We successfully isolated two MuSK-specific IgG4 subclass-expressing plasmablasts from two of these patients, who were experiencing a relapse after a BCDT-induced remission. Human recombinant MuSK mAbs were then generated to validate binding specificity and characterize their molecular properties. Both mAbs were strong MuSK binders, they recognized the Ig1-like domain of MuSK, and showed pathogenic capacity when tested in an acetylcholine receptor (AChR) clustering assay. The presence of persistent clonal relatives of these MuSK-specific B cell clones was investigated through B cell receptor repertoire tracing of 63,977 unique clones derived from longitudinal samples collected from these two patients. Clonal variants were detected at multiple timepoints spanning more than five years and reemerged after BCDT-mediated remission, predating disease relapse by several months. These findings demonstrate that a reservoir of rare pathogenic MuSK autoantibody-expressing B cell clones survive BCDT and reemerge into circulation prior to manifestation of clinical relapse. Overall, this study provides both a mechanistic understanding of MuSK MG relapse and a valuable candidate biomarker for relapse prediction.
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Affiliation(s)
- Miriam L Fichtner
- Department of Neurology, Yale University School of Medicine, 300 George Street - Room 353J, New Haven, CT, 06511, USA
- Department of Immunobiology, Yale University School of Medicine, 300 George Street - Room 353J, New Haven, CT, 06511, USA
| | - Kenneth B Hoehn
- Department of Pathology, Yale School of Medicine, New Haven, CT, USA
| | - Easton E Ford
- Department of Microbiology and Immunology, University of Louisville School of Medicine, Louisville, KY, USA
| | - Marina Mane-Damas
- Department of Psychiatry and Neuropsychology, School for Mental Health and Neuroscience, Maastricht University, Maastricht, The Netherlands
| | - Sangwook Oh
- Department of Dermatology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Patrick Waters
- Oxford Autoimmune Neurology Group, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - Aimee S Payne
- Department of Dermatology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Melissa L Smith
- Department of Microbiology and Immunology, University of Louisville School of Medicine, Louisville, KY, USA
- Department of Biochemistry and Molecular Genetics, University of Louisville School of Medicine, Louisville, KY, USA
| | - Corey T Watson
- Department of Microbiology and Immunology, University of Louisville School of Medicine, Louisville, KY, USA
- Department of Biochemistry and Molecular Genetics, University of Louisville School of Medicine, Louisville, KY, USA
| | - Mario Losen
- Department of Psychiatry and Neuropsychology, School for Mental Health and Neuroscience, Maastricht University, Maastricht, The Netherlands
| | - Pilar Martinez-Martinez
- Department of Psychiatry and Neuropsychology, School for Mental Health and Neuroscience, Maastricht University, Maastricht, The Netherlands
| | - Richard J Nowak
- Department of Neurology, Yale University School of Medicine, 300 George Street - Room 353J, New Haven, CT, 06511, USA
| | - Steven H Kleinstein
- Department of Immunobiology, Yale University School of Medicine, 300 George Street - Room 353J, New Haven, CT, 06511, USA
- Department of Pathology, Yale School of Medicine, New Haven, CT, USA
- Program in Computational Biology & Bioinformatics, Yale University, New Haven, CT, USA
| | - Kevin C O'Connor
- Department of Neurology, Yale University School of Medicine, 300 George Street - Room 353J, New Haven, CT, 06511, USA.
- Department of Immunobiology, Yale University School of Medicine, 300 George Street - Room 353J, New Haven, CT, 06511, USA.
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17
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Jentzer A, Attal A, Roué C, Raymond J, Lleixà C, Illa I, Querol L, Taieb G, Devaux J. IgG4 Valency Modulates the Pathogenicity of Anti–Neurofascin-155 IgG4 in Autoimmune Nodopathy. NEUROLOGY - NEUROIMMUNOLOGY NEUROINFLAMMATION 2022; 9:9/5/e200014. [PMID: 35948442 PMCID: PMC9365386 DOI: 10.1212/nxi.0000000000200014] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/10/2022] [Accepted: 05/18/2022] [Indexed: 12/03/2022]
Abstract
Background and Objectives IgG4 autoantibodies to neurofascin-155 (Nfasc155) are associated with a subgroup of patients with chronic inflammatory demyelinating polyneuropathy (CIDP), currently named autoimmune nodopathy. We previously demonstrated that those antibodies alter conduction along myelinated axons by inducing Nfasc155 depletion and paranode destruction. In blood, IgG4 have the potency to exchange their moiety with other unrelated IgG4 through a process called Fab-arm exchange (FAE). This process results in functionally monovalent antibodies and may affect the pathogenicity of autoantibodies. Here, we examined this issue and whether FAE is beneficial or detrimental for Nfasc155 autoimmune nodopathy. Methods The bivalency and monospecificity of anti-Nfasc155 were examined by sandwich ELISA in 10 reactive patients, 10 unreactive CIDP patients, and 10 healthy controls. FAE was induced in vitro using reduced glutathione and unreactive IgG4, and the ratio of the κ:λ light chain was monitored. To determine the pathogenic potential of bivalent anti-Nfasc155 IgG4, autoantibodies derived from patients were enzymatically cleaved into monovalent Fab and bivalent F(ab’)2 or swapped with unreactive IgG4 and then were injected in neonatal animals. Results Monospecific bivalent IgG4 against Nfasc155 were detected in the serum of all reactive patients, indicating that a fraction of IgG4 have not undergone FAE in situ. These IgG4 were, nonetheless, capable of engaging into FAE with unreactive IgG4 in vitro, and this decreased the levels of monospecific antibodies and modulated the ratio of the κ:λ light chain. When injected in animals, monovalent anti-Nfasc155 Fab did not alter the formation of paranodes; by contrast, both native anti-Nfasc155 IgG4 and F(ab’)2 fragments strongly impaired paranode formation. The promotion of FAE with unreactive IgG4 also strongly diminished the pathogenic potential of anti-Nfasc155 IgG4 in animals and decreased IgG4 clustering on Schwann cells. Discussion Our findings demonstrate that monospecific and bivalent anti-Nfasc155 IgG4 are detected in patients and that those autoantibodies are the pathogenic ones. The transformation of anti-Nfasc155 IgG4 into monovalent Fab or functionally monovalent IgG4 through FAE strongly decreases paranodal alterations. Bivalency thus appears crucial for Nfasc155 clustering and paranode destruction.
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Affiliation(s)
- Alexandre Jentzer
- From the Institute for Neurosciences of Montpellier (A.J., A.A., G.T., J.D.), INSERM U1051, Montpellier University, Hôpital Saint Eloi, France; Department of Immunology (A.J.), CHU Montpellier, France ; Department of Neurology (A.A., G.T.), CHU Montpellier, Hôpital Gui de Chauliac, France; Institut de Génomique Fonctionnelle (C.R., J.R., G.T., J.D.), CNRS UMR5203, France; and Neuromuscular Diseases Unit (C.L., I.I., L.Q.), Hospital de la Santa Creu i Sant Pau, Universitat Autónoma de Barcelona, Spain
| | - Arthur Attal
- From the Institute for Neurosciences of Montpellier (A.J., A.A., G.T., J.D.), INSERM U1051, Montpellier University, Hôpital Saint Eloi, France; Department of Immunology (A.J.), CHU Montpellier, France ; Department of Neurology (A.A., G.T.), CHU Montpellier, Hôpital Gui de Chauliac, France; Institut de Génomique Fonctionnelle (C.R., J.R., G.T., J.D.), CNRS UMR5203, France; and Neuromuscular Diseases Unit (C.L., I.I., L.Q.), Hospital de la Santa Creu i Sant Pau, Universitat Autónoma de Barcelona, Spain
| | - Clémence Roué
- From the Institute for Neurosciences of Montpellier (A.J., A.A., G.T., J.D.), INSERM U1051, Montpellier University, Hôpital Saint Eloi, France; Department of Immunology (A.J.), CHU Montpellier, France ; Department of Neurology (A.A., G.T.), CHU Montpellier, Hôpital Gui de Chauliac, France; Institut de Génomique Fonctionnelle (C.R., J.R., G.T., J.D.), CNRS UMR5203, France; and Neuromuscular Diseases Unit (C.L., I.I., L.Q.), Hospital de la Santa Creu i Sant Pau, Universitat Autónoma de Barcelona, Spain
| | - Julie Raymond
- From the Institute for Neurosciences of Montpellier (A.J., A.A., G.T., J.D.), INSERM U1051, Montpellier University, Hôpital Saint Eloi, France; Department of Immunology (A.J.), CHU Montpellier, France ; Department of Neurology (A.A., G.T.), CHU Montpellier, Hôpital Gui de Chauliac, France; Institut de Génomique Fonctionnelle (C.R., J.R., G.T., J.D.), CNRS UMR5203, France; and Neuromuscular Diseases Unit (C.L., I.I., L.Q.), Hospital de la Santa Creu i Sant Pau, Universitat Autónoma de Barcelona, Spain
| | - Cinta Lleixà
- From the Institute for Neurosciences of Montpellier (A.J., A.A., G.T., J.D.), INSERM U1051, Montpellier University, Hôpital Saint Eloi, France; Department of Immunology (A.J.), CHU Montpellier, France ; Department of Neurology (A.A., G.T.), CHU Montpellier, Hôpital Gui de Chauliac, France; Institut de Génomique Fonctionnelle (C.R., J.R., G.T., J.D.), CNRS UMR5203, France; and Neuromuscular Diseases Unit (C.L., I.I., L.Q.), Hospital de la Santa Creu i Sant Pau, Universitat Autónoma de Barcelona, Spain
| | - Isabel Illa
- From the Institute for Neurosciences of Montpellier (A.J., A.A., G.T., J.D.), INSERM U1051, Montpellier University, Hôpital Saint Eloi, France; Department of Immunology (A.J.), CHU Montpellier, France ; Department of Neurology (A.A., G.T.), CHU Montpellier, Hôpital Gui de Chauliac, France; Institut de Génomique Fonctionnelle (C.R., J.R., G.T., J.D.), CNRS UMR5203, France; and Neuromuscular Diseases Unit (C.L., I.I., L.Q.), Hospital de la Santa Creu i Sant Pau, Universitat Autónoma de Barcelona, Spain
| | - Luis Querol
- From the Institute for Neurosciences of Montpellier (A.J., A.A., G.T., J.D.), INSERM U1051, Montpellier University, Hôpital Saint Eloi, France; Department of Immunology (A.J.), CHU Montpellier, France ; Department of Neurology (A.A., G.T.), CHU Montpellier, Hôpital Gui de Chauliac, France; Institut de Génomique Fonctionnelle (C.R., J.R., G.T., J.D.), CNRS UMR5203, France; and Neuromuscular Diseases Unit (C.L., I.I., L.Q.), Hospital de la Santa Creu i Sant Pau, Universitat Autónoma de Barcelona, Spain
| | - Guillaume Taieb
- From the Institute for Neurosciences of Montpellier (A.J., A.A., G.T., J.D.), INSERM U1051, Montpellier University, Hôpital Saint Eloi, France; Department of Immunology (A.J.), CHU Montpellier, France ; Department of Neurology (A.A., G.T.), CHU Montpellier, Hôpital Gui de Chauliac, France; Institut de Génomique Fonctionnelle (C.R., J.R., G.T., J.D.), CNRS UMR5203, France; and Neuromuscular Diseases Unit (C.L., I.I., L.Q.), Hospital de la Santa Creu i Sant Pau, Universitat Autónoma de Barcelona, Spain
| | - Jérôme Devaux
- From the Institute for Neurosciences of Montpellier (A.J., A.A., G.T., J.D.), INSERM U1051, Montpellier University, Hôpital Saint Eloi, France; Department of Immunology (A.J.), CHU Montpellier, France ; Department of Neurology (A.A., G.T.), CHU Montpellier, Hôpital Gui de Chauliac, France; Institut de Génomique Fonctionnelle (C.R., J.R., G.T., J.D.), CNRS UMR5203, France; and Neuromuscular Diseases Unit (C.L., I.I., L.Q.), Hospital de la Santa Creu i Sant Pau, Universitat Autónoma de Barcelona, Spain.
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18
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Oostindie SC, Lazar GA, Schuurman J, Parren PWHI. Avidity in antibody effector functions and biotherapeutic drug design. Nat Rev Drug Discov 2022; 21:715-735. [PMID: 35790857 PMCID: PMC9255845 DOI: 10.1038/s41573-022-00501-8] [Citation(s) in RCA: 64] [Impact Index Per Article: 32.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/30/2022] [Indexed: 12/16/2022]
Abstract
Antibodies are the cardinal effector molecules of the immune system and are being leveraged with enormous success as biotherapeutic drugs. A key part of the adaptive immune response is the production of an epitope-diverse, polyclonal antibody mixture that is capable of neutralizing invading pathogens or disease-causing molecules through binding interference and by mediating humoral and cellular effector functions. Avidity - the accumulated binding strength derived from the affinities of multiple individual non-covalent interactions - is fundamental to virtually all aspects of antibody biology, including antibody-antigen binding, clonal selection and effector functions. The manipulation of antibody avidity has since emerged as an important design principle for enhancing or engineering novel properties in antibody biotherapeutics. In this Review, we describe the multiple levels of avidity interactions that trigger the overall efficacy and control of functional responses in both natural antibody biology and their therapeutic applications. Within this framework, we comprehensively review therapeutic antibody mechanisms of action, with particular emphasis on engineered optimizations and platforms. Overall, we describe how affinity and avidity tuning of engineered antibody formats are enabling a new wave of differentiated antibody drugs with tailored properties and novel functions, promising improved treatment options for a wide variety of diseases.
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Affiliation(s)
- Simone C Oostindie
- Genmab, Utrecht, Netherlands.,Department of Immunology, Leiden University Medical Center, Leiden, Netherlands
| | - Greg A Lazar
- Department of Antibody Engineering, Genentech, San Francisco, CA, USA
| | | | - Paul W H I Parren
- Department of Immunology, Leiden University Medical Center, Leiden, Netherlands. .,Sparring Bioconsult, Odijk, Netherlands. .,Lava Therapeutics, Utrecht, Netherlands.
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19
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Orchestration of Immune Cells Contributes to Fibrosis in IgG4-Related Disease. IMMUNO 2022. [DOI: 10.3390/immuno2010013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
This review summarizes recent progress in understanding the pathogenesis of IgG4-related disease (IgG4-RD), with a focus on fibrosis. Several studies reported that CD4+ T cells with cytotoxic activity promoted by the secretion of granzyme and perforin, cytotoxic CD4+ T cells (CD4+CTLs), and disease-specific activated B cells, infiltrated inflamed tissues and cooperated to induce tissue fibrosis in autoimmune fibrotic diseases such as IgG4-RD, systemic sclerosis, and fibrosing mediastinitis. An accumulation of cells undergoing apoptotic cell death induced by CD4+CTLs and CD8+CTLs followed by macrophage-mediated clearing and finally tissue remodeling driven by cytokines released by CD4+CTLs, activated B cells, and M2 macrophages may contribute to the activation of fibroblasts and collagen production. In IgG4-RD, this process likely involves the apoptosis of non-immune, non-endothelial cells of mesenchymal origin and subsequent tissue remodeling. In summary, CD4+CTLs infiltrate affected tissues where they may cooperate with activated B cells, CD8+CTLs, and M2 macrophages, to induce apoptosis by secreting cytotoxic cytokines. These immune cells also drive fibrosis by secreting pro-fibrotic molecules in IgG4-RD.
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20
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Huijbers MG, Marx A, Plomp JJ, Le Panse R, Phillips WD. Advances in the understanding of disease mechanisms of autoimmune neuromuscular junction disorders. Lancet Neurol 2022; 21:163-175. [DOI: 10.1016/s1474-4422(21)00357-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2021] [Revised: 09/15/2021] [Accepted: 10/06/2021] [Indexed: 01/19/2023]
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21
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Treger RS, Fink SL. Beyond Titer: Expanding the Scope of Clinical Autoantibody Testing. J Appl Lab Med 2022; 7:99-113. [DOI: 10.1093/jalm/jfab123] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2021] [Accepted: 09/17/2021] [Indexed: 11/14/2022]
Abstract
Abstract
Background
Autoantibodies that bind self-antigens are a hallmark of autoimmune diseases, but can also be present in healthy individuals. Clinical assays that detect and titer antigen-specific autoantibodies are an important component of the diagnosis and monitoring of autoimmune diseases. Autoantibodies may contribute to disease pathogenesis via effector functions that are dictated by both the antigen-binding site and constant domain.
Content
In this review, we discuss features of antibodies, in addition to antigen-binding specificity, which determine effector function. These features include class, subclass, allotype, and glycosylation. We discuss emerging data indicating that analysis of these antibody features may be informative for diagnosis and monitoring of autoimmune diseases. We also consider methodologies to interrogate these features and consider how they could be implemented in the clinical laboratory.
Summary
Future autoantibody assays may incorporate assessment of additional antibody features that contribute to autoimmune disease pathogenesis and provide added clinical value.
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Affiliation(s)
- Rebecca S Treger
- Department of Laboratory Medicine and Pathology, University of Washington, Seattle, WA, USA
| | - Susan L Fink
- Department of Laboratory Medicine and Pathology, University of Washington, Seattle, WA, USA
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22
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Liu J, Yin W, Westerberg LS, Lee P, Gong Q, Chen Y, Dong L, Liu C. Immune Dysregulation in IgG 4-Related Disease. Front Immunol 2021; 12:738540. [PMID: 34539675 PMCID: PMC8440903 DOI: 10.3389/fimmu.2021.738540] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2021] [Accepted: 08/09/2021] [Indexed: 12/26/2022] Open
Abstract
Immunoglobin G4-related disease (IgG4-RD) is one of the newly discovered autoimmune diseases characterized by elevated serum IgG4 concentrations and multi-organ fibrosis. Despite considerable research and recent advances in the identification of underlying immunological processes, the etiology of this disease is still not clear. Adaptive immune cells, including different types of T and B cells, and cytokines secreted by these cells play a vital role in the pathogenesis of IgG4-RD. Antigen-presenting cells are stimulated by pathogens and, thus, contribute to the activation of naïve T cells and differentiation of different T cell subtypes, including helper T cells (Th1 and Th2), regulatory T cells, and T follicular helper cells. B cells are activated and transformed to plasma cells by T cell-secreted cytokines. Moreover, macrophages, and some important factors (TGF-β, etc.) promote target organ fibrosis. Understanding the role of these cells and cytokines implicated in the pathogenesis of IgG4-RD will aid in developing strategies for future disease treatment and drug development. Here, we review the most recent insights on IgG4-RD, focusing on immune dysregulation involved in the pathogenesis of this autoimmune condition.
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Affiliation(s)
- Jiachen Liu
- Department of Pathogen Biology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Wei Yin
- Wuhan Children's Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Lisa S Westerberg
- Department of Microbiology Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden
| | - Pamela Lee
- Department of Paediatrics and Adolescent Medicine, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
| | - Quan Gong
- Department of Immunology, School of Medicine, Yangtze University, Jingzhou, China
| | - Yan Chen
- The Second Department of Pediatrics, Affiliated Hospital of Zunyi Medical University, Zunyi, China
| | - Lingli Dong
- Department of Rheumatology and Immunology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Chaohong Liu
- Department of Pathogen Biology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
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23
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Basile U, Napodano C, Gulli F, Pocino K, Di Santo R, Todi L, Basile V, Provenzano C, Ciasca G, Marino M. Laboratory Investigation of Hybrid IgG4 k/λ in MuSK Positive Myasthenia Gravis. Int J Mol Sci 2021; 22:ijms22179142. [PMID: 34502051 PMCID: PMC8430634 DOI: 10.3390/ijms22179142] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2021] [Revised: 08/03/2021] [Accepted: 08/14/2021] [Indexed: 12/29/2022] Open
Abstract
Myasthenia gravis with antibodies (Abs) against the muscle-specific tyrosine kinase (MuSK) is a rare autoimmune disorder (AD) of the neuromuscular junction (NMJ) and represents a prototype of AD with proven IgG4-mediated pathogenicity. Thanks to the mechanism of Fab-arm exchange (FAE) occurring in vivo, resulting MuSK IgG4 k/λ Abs increase their interference on NMJ and pathogenicity. The characterization of hybrid MuSK IgG4 as a biomarker for MG management is poorly investigated. Here, we evaluated total IgG4, hybrid IgG4 k/λ, and the hybrid/total ratio in 14 MuSK-MG sera in comparison with 24 from MG with Abs against acetylcholine receptor (AChR) that represents the not IgG4-mediated MG form. In both subtypes of MG, we found that the hybrid/total ratio reflects distribution reported in normal individuals; instead, when we correlated the hybrid/total ratio with specific immune-reactivity we found a positive correlation only with anti-MuSK titer, with a progressive increase of hybrid/total mean values with increasing disease severity, indirectly confirming that most part of hybrid IgG4 molecules are engaged in the anti-MuSK pathogenetic immune-reactivity. Further analysis is necessary to strengthen the significance of this less unknown biomarker, but we retain it is full of a diagnostic-prognostic powerful potential for the management of MuSK-MG.
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Affiliation(s)
- Umberto Basile
- Dipartimento di Scienze di Laboratorio e Infettivologiche, Fondazione Policlinico Universitario “A. Gemelli” IRCCS, Università Cattolica del Sacro Cuore, 00168 Rome, Italy;
| | | | - Francesca Gulli
- Laboratorio di Patologia Clinica, Ospedale Madre Giuseppina Vannini, 00177 Rome, Italy;
| | - Krizia Pocino
- Unità Operativa Complessa Patologia Clinica, Ospedale Generale di Zona, San Pietro Fatebenefratelli, 00189 Rome, Italy;
| | - Riccardo Di Santo
- Dipartimento di Neuroscienze, Sezione di Fisica, Fondazione Policlinico “A. Gemelli” IRCCS, Università Cattolica del Sacro Cuore, 00168 Rome, Italy; (R.D.S.); (G.C.)
| | - Laura Todi
- Dipartimento di Medicina e Chirurgia Traslazionale, Sezione di Patologia Generale, Fondazione Policlinico Universitario “A. Gemelli” IRCCS, Università Cattolica del Sacro Cuore, 00168 Rome, Italy; (L.T.); (C.P.)
| | - Valerio Basile
- Clinical Pathology Unit and Cancer Biobank, Department of Research, Advanced Diagnostics and Technological Innovation, IFO-Regina Elena National Cancer Institute, 00128 Rome, Italy;
| | - Carlo Provenzano
- Dipartimento di Medicina e Chirurgia Traslazionale, Sezione di Patologia Generale, Fondazione Policlinico Universitario “A. Gemelli” IRCCS, Università Cattolica del Sacro Cuore, 00168 Rome, Italy; (L.T.); (C.P.)
| | - Gabriele Ciasca
- Dipartimento di Neuroscienze, Sezione di Fisica, Fondazione Policlinico “A. Gemelli” IRCCS, Università Cattolica del Sacro Cuore, 00168 Rome, Italy; (R.D.S.); (G.C.)
| | - Mariapaola Marino
- Dipartimento di Medicina e Chirurgia Traslazionale, Sezione di Patologia Generale, Fondazione Policlinico Universitario “A. Gemelli” IRCCS, Università Cattolica del Sacro Cuore, 00168 Rome, Italy; (L.T.); (C.P.)
- Correspondence:
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