1
|
Pham MC, Masi G, Patzina R, Obaid AH, Oxendine SR, Oh S, Payne AS, Nowak RJ, O'Connor KC. Individual myasthenia gravis autoantibody clones can efficiently mediate multiple mechanisms of pathology. Acta Neuropathol 2023; 146:319-336. [PMID: 37344701 DOI: 10.1007/s00401-023-02603-y] [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: 01/05/2023] [Revised: 06/15/2023] [Accepted: 06/16/2023] [Indexed: 06/23/2023]
Abstract
Serum autoantibodies targeting the nicotinic acetylcholine receptor (AChR) in patients with autoimmune myasthenia gravis (MG) can mediate pathology via three distinct molecular mechanisms: complement activation, receptor blockade, and antigenic modulation. However, it is unclear whether multi-pathogenicity is mediated by individual or multiple autoantibody clones. Using an unbiased B cell culture screening approach, we generated a library of 11 human-derived AChR-specific recombinant monoclonal autoantibodies (mAb) and assessed their binding properties and pathogenic profiles using specialized cell-based assays. Five mAbs activated complement, three blocked α-bungarotoxin binding to the receptor, and seven induced antigenic modulation. Furthermore, two clonally related mAbs derived from one patient were each highly efficient at more than one of these mechanisms, demonstrating that pathogenic mechanisms are not mutually exclusive at the monoclonal level. Using novel Jurkat cell lines that individually express each monomeric AChR subunit (α2βδε), these two mAbs with multi-pathogenic capacity were determined to exclusively bind the α-subunit of AChR, demonstrating an association between mAb specificity and pathogenic capacity. These findings provide new insight into the immunopathology of MG, demonstrating that single autoreactive clones can efficiently mediate multiple modes of pathology. Current therapeutic approaches targeting only one autoantibody-mediated pathogenic mechanism may be evaded by autoantibodies with multifaceted capacity.
Collapse
Affiliation(s)
- Minh C Pham
- Department of Immunobiology, Yale University School of Medicine, 300 George Street-Room 353J, New Haven, CT, 06511, USA
| | - Gianvito Masi
- Department of Immunobiology, Yale University School of Medicine, 300 George Street-Room 353J, New Haven, CT, 06511, USA
- Department of Neurology, Yale University School of Medicine, New Haven, CT, 06511, USA
| | - Rosa Patzina
- Department of Immunobiology, Yale University School of Medicine, 300 George Street-Room 353J, New Haven, CT, 06511, USA
- Department of Neurology, Yale University School of Medicine, New Haven, CT, 06511, USA
| | - Abeer H Obaid
- Department of Immunobiology, Yale University School of Medicine, 300 George Street-Room 353J, New Haven, CT, 06511, USA
- Department of Neurology, Yale University School of Medicine, New Haven, CT, 06511, USA
- Institute of Biomedical Studies, Baylor University, Waco, TX, 76706, USA
| | - Seneca R Oxendine
- Department of Immunobiology, Yale University School of Medicine, 300 George Street-Room 353J, New Haven, CT, 06511, USA
- Department of Neurology, Yale University School of Medicine, New Haven, CT, 06511, USA
| | - Sangwook Oh
- Department of Dermatology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Aimee S Payne
- Department of Dermatology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Richard J Nowak
- Department of Neurology, Yale University School of Medicine, New Haven, CT, 06511, USA
| | - Kevin C O'Connor
- Department of Immunobiology, Yale University School of Medicine, 300 George Street-Room 353J, New Haven, CT, 06511, USA.
- Department of Neurology, Yale University School of Medicine, New Haven, CT, 06511, USA.
| |
Collapse
|
2
|
Yan C, Zhao R, Song J, Feng X, Xi J, Luo S, Zhong H, Zhou S, Li W, Zhao C. Comparison of anti-acetylcholine receptor profiles between Chinese cases of adult- and juvenile-onset myasthenia gravis using cell-based assays. J Neuroimmunol 2020; 349:577403. [PMID: 32992216 DOI: 10.1016/j.jneuroim.2020.577403] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2020] [Revised: 08/29/2020] [Accepted: 09/19/2020] [Indexed: 10/23/2022]
Abstract
OBJECTIVE Juvenile-onset myasthenia gravis (JOMG) is a unique clinical subtype in China, featured by a higher prevalence of ocular myasthenia gravis (OMG), higher seronegativity of acetylcholine receptor (AChR) antibodies, and better prognosis than that in adult-onset myasthenia gravis (AOMG). We previously identified low-affinity AChR antibodies in Chinese JOMG patients using cell-based assays (CBAs), indicating a predominantly AChR antibody-positive profile. Here, we further screened AChR antibodies in both Chinese AOMG and JOMG patients by CBAs. MATERIALS AND METHODS We recruited patients with MG who had not received prednisone or immunosuppressive therapies between June 2015 and June 2019, and divided them into AOMG and JOMG subgroups according to their ages at the time of recruitment. Clinical information and blood samples were collected. Serum AChR antibodies were detected by CBAs in HEK293T cells expressing clustered adult and fetal AChRs, as well as by enzyme-linked immunosorbent assays (ELISAs). Differences in AChR antibody profiles between AOMG and JOMG subgroups were determined. RESULTS A total of 239 patients with MG were enrolled in the present study, including 121 AOMG and 118 JOMG patients. Based on ELISAs, 74.4% of AOMG (90/121) and 59.3% of JOMG (70/118) patients were anti-AChR positive (p = 0.02). However, CBAs yielded equal anti-AChR positivities (p = 0.64), as indicated by 80.2% of AOMG patients (97/121) and 77.1% of JOMG patients (91/118). Furthermore, among AOMG patients, 67.8% (82/121) were positive for both adult and fetal AChR antibodies, 5.8% (7/121) were positive for only adult AChR antibodies, and 6.6% (8/121) were positive for only fetal AChR antibodies, while these rates were 50.8% (60/118), 21.2% (25/118), and 5.1% (6/118), respectively, in JOMG cohorts (p < 0.01). Twenty-nine AOMG patients and 10 JOMG patients underwent IgG subclassification of AChR antibodies, which were all confirmed to be predominantly IgG1. CONCLUSIONS The positive rates of AChR antibodies did not differ between Chinese AOMG and JOMG patients, as revealed by CBAs. Furthermore, the screened AChR antibodies were predominantly IgG1 in both AOMG and JOMG patients.
Collapse
Affiliation(s)
- Chong Yan
- Department of Neurology, Huashan Hospital, Fudan University, Shanghai 200040, China
| | - Rui Zhao
- Department of Neurology, Huashan Hospital, Fudan University, Shanghai 200040, China
| | - Jie Song
- Department of Neurology, Huashan Hospital, Fudan University, Shanghai 200040, China
| | - Xuelin Feng
- Department of Neurology, The First Affiliated Hospital, Sun Yat-sen University, Guangdong 510080, China
| | - Jianying Xi
- Department of Neurology, Huashan Hospital, Fudan University, Shanghai 200040, China
| | - Sushan Luo
- Department of Neurology, Huashan Hospital, Fudan University, Shanghai 200040, China
| | - Huahua Zhong
- Department of Neurology, Huashan Hospital, Fudan University, Shanghai 200040, China
| | - Shuizhen Zhou
- Department of Neurology, Children's Hospital of Fudan University, Shanghai 200040, China
| | - Wenhui Li
- Department of Neurology, Children's Hospital of Fudan University, Shanghai 200040, China.
| | - Chongbo Zhao
- Department of Neurology, Huashan Hospital, Fudan University, Shanghai 200040, China; Department of Neurology, Jing'an District Center Hospital of Shanghai, Fudan University, Shanghai 200040, China.
| |
Collapse
|
3
|
Cetin H, Webster R, Liu WW, Nagaishi A, Koneczny I, Zimprich F, Maxwell S, Cossins J, Beeson D, Vincent A. Myasthenia gravis AChR antibodies inhibit function of rapsyn-clustered AChRs. J Neurol Neurosurg Psychiatry 2020; 91:526-532. [PMID: 32165373 PMCID: PMC7231439 DOI: 10.1136/jnnp-2019-322640] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/15/2019] [Revised: 02/24/2020] [Accepted: 02/25/2020] [Indexed: 11/27/2022]
Abstract
OBJECTIVE Direct inhibition of acetylcholine receptor (AChR) function by autoantibodies (Abs) is considered a rare pathogenic mechanism in myasthenia gravis (MG), but is usually studied on AChRs expressed in cell lines, rather than tightly clustered by the intracellular scaffolding protein, rapsyn, as at the intact neuromuscular junction. We hypothesised that clustered AChRs would provide a better target for investigating the functional effects of AChR-Abs. METHODS Acetylcholine-induced currents were measured using whole-cell patch clamping and a fast perfusion system to assess fast (<2 min) functional effects of the serum samples. The sensitivity, specificity and rapidity of the system were first demonstrated by applying maternal AChR-Ab positive plasmas known to inhibit fetal AChR function in TE671 cells. Eleven previously untested AChR-Ab positive MG sera, 10 AChR-Ab negative MG sera and 5 healthy control sera were then applied to unclustered and rapsyn-clustered human adult AChRs in CN21 cells. RESULTS The maternal AChR-Ab positive plasmas reduced fetal AChR currents, but not adult AChR currents, by >80% within 100 s. Only 2/11 AChR-Ab positive sera inhibited AChR currents in unclustered AChRs, but 6/11 AChR-Ab positive sera compared with none of the 10 AChR-Ab negative sera (p=0.0020) inhibited rapsyn-clustered AChR currents, and current inhibition by the AChR-Ab positive sera was greater when the AChRs were clustered (p=0.0385). None of the sera had detectable effects on desensitisation or recovery from desensitisation. CONCLUSION These results show that antibodies can inhibit AChR function rapidly and demonstrate the importance of clustering in exploring pathogenic disease mechanisms of MG Abs.
Collapse
Affiliation(s)
- Hakan Cetin
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, Oxfordshire, UK.,Department of Neurology, Medical University of Vienna, Vienna, Austria
| | - Richard Webster
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, Oxfordshire, UK
| | - Wei Wei Liu
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, Oxfordshire, UK
| | - Akiko Nagaishi
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, Oxfordshire, UK
| | - Inga Koneczny
- Institute of Neurology, Medical University of Vienna, Vienna, Austria
| | - Fritz Zimprich
- Department of Neurology, Medical University of Vienna, Vienna, Austria
| | - Susan Maxwell
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, Oxfordshire, UK
| | - Judith Cossins
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, Oxfordshire, UK
| | - David Beeson
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, Oxfordshire, UK
| | - Angela Vincent
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, Oxfordshire, UK
| |
Collapse
|
4
|
Vincent A, Huda S, Cao M, Cetin H, Koneczny I, Rodriguez Cruz PM, Jacobson L, Viegas S, Jacob S, Woodhall M, Nagaishi A, Maniaol A, Damato V, Leite MI, Cossins J, Webster R, Palace J, Beeson D. Serological and experimental studies in different forms of myasthenia gravis. Ann N Y Acad Sci 2018; 1413:143-153. [PMID: 29377162 DOI: 10.1111/nyas.13592] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2017] [Revised: 12/11/2017] [Accepted: 12/12/2017] [Indexed: 12/11/2022]
Abstract
Antibodies to the acetylcholine receptor (AChR) have been recognized for over 40 years and have been important in the diagnosis of myasthenia gravis (MG), and its recognition in patients of different ages and thymic pathologies. The 10-20% of patients who do not have AChR antibodies are now known to comprise different subgroups, the most commonly reported of which is patients with antibodies to muscle-specific kinase (MuSK). The use of cell-based assays has extended the repertoire of antibody tests to clustered AChRs, low-density lipoprotein receptor-related protein 4, and agrin. Autoantibodies against intracellular targets, namely cortactin, titin, and ryanodine receptor (the latter two being associated with the presence of thymoma), may also be helpful as biomarkers in some patients. IgG4 MuSK antibodies are clearly pathogenic, but the coexisting IgG1, IgG2, and IgG3 antibodies, collectively, have effects that question the dominance of IgG4 as the sole pathologic factor in MuSK MG. After a brief historical review, we define the different subgroups and summarize the antibody characteristics. Experiments to demonstrate the in vitro and in vivo pathogenic roles of MuSK antibodies are discussed.
Collapse
Affiliation(s)
- Angela Vincent
- Neuroimmunology Group, Nuffield Department of Clinical Neurosciences, Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, University of Oxford, Oxford, UK
| | - Saif Huda
- Neuroimmunology Group, Nuffield Department of Clinical Neurosciences, Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, University of Oxford, Oxford, UK
| | - Michelangelo Cao
- Neuroimmunology Group, Nuffield Department of Clinical Neurosciences, Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, University of Oxford, Oxford, UK
| | - Hakan Cetin
- Neuroimmunology Group, Nuffield Department of Clinical Neurosciences, Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, University of Oxford, Oxford, UK
| | - Inga Koneczny
- Neuroimmunology Group, Nuffield Department of Clinical Neurosciences, Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, University of Oxford, Oxford, UK
| | - Pedro M Rodriguez Cruz
- Neuroimmunology Group, Nuffield Department of Clinical Neurosciences, Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, University of Oxford, Oxford, UK
| | - Leslie Jacobson
- Neuroimmunology Group, Nuffield Department of Clinical Neurosciences, Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, University of Oxford, Oxford, UK
| | - Stuart Viegas
- Neuroimmunology Group, Nuffield Department of Clinical Neurosciences, Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, University of Oxford, Oxford, UK
| | - Saiju Jacob
- Neuroimmunology Group, Nuffield Department of Clinical Neurosciences, Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, University of Oxford, Oxford, UK
| | - Mark Woodhall
- Neuroimmunology Group, Nuffield Department of Clinical Neurosciences, Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, University of Oxford, Oxford, UK
| | - Akiko Nagaishi
- Neuroimmunology Group, Nuffield Department of Clinical Neurosciences, Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, University of Oxford, Oxford, UK
| | - Angelina Maniaol
- Neuroimmunology Group, Nuffield Department of Clinical Neurosciences, Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, University of Oxford, Oxford, UK
| | - Valentina Damato
- Neuroimmunology Group, Nuffield Department of Clinical Neurosciences, Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, University of Oxford, Oxford, UK
| | - M Isabel Leite
- Neuroimmunology Group, Nuffield Department of Clinical Neurosciences, Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, University of Oxford, Oxford, UK
| | - Judith Cossins
- Neuroimmunology Group, Nuffield Department of Clinical Neurosciences, Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, University of Oxford, Oxford, UK
| | - Richard Webster
- Neuroimmunology Group, Nuffield Department of Clinical Neurosciences, Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, University of Oxford, Oxford, UK
| | - Jacqueline Palace
- Neuroimmunology Group, Nuffield Department of Clinical Neurosciences, Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, University of Oxford, Oxford, UK
| | - David Beeson
- Neuroimmunology Group, Nuffield Department of Clinical Neurosciences, Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, University of Oxford, Oxford, UK
| |
Collapse
|
5
|
Lang B, Willcox N. Autoantibodies in neuromuscular autoimmune disorders. Expert Rev Clin Immunol 2014; 2:293-307. [DOI: 10.1586/1744666x.2.2.293] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
|
6
|
Vincent A. John Newsom-Davis: clinician-scientist and so much more. Brain 2011; 134:3755-74. [PMID: 22171357 PMCID: PMC3235562 DOI: 10.1093/brain/awr284] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2011] [Revised: 09/07/2011] [Accepted: 09/08/2011] [Indexed: 01/17/2023] Open
Abstract
John Newsom-Davis was born in 1932 and died, aged 74, in 2007. After national service in the Royal Air Force, he read Natural Sciences at Cambridge. Following clinical studies at the Middlesex Hospital, he began research into respiratory neurophysiology with Tom Sears at the National Hospital, Queen Square, in London, and spent 1 year with Fred Plum at Cornell University in New York. After neurology specialist training at Queen Square, he became the director of the Batten Unit, continuing his interest in respiratory physiology. There he began to work on myasthenia gravis in collaboration with Ricardo Miledi at University College London and in 1978, after performing the first studies on plasma exchange in that disease, he established a myasthenia gravis research group at the Royal Free Hospital. There he investigated the role of the thymus in this disease and demonstrated an autoimmune basis for the Lambert Eaton myasthenic syndrome and 'seronegative' myasthenia. He was awarded the first Medical Research Council Clinical Research Professorship in 1979 but moved to Oxford in 1987 when he was elected Action Research Professor of Neurology. While at Oxford, he continued to run a very successful multidisciplinary group, researched further into the thymic abnormalities and cellular immunology of myasthenia, identified antibody-mediated mechanisms in acquired neuromyotonia, and began the molecular work that identified the genetic basis for many forms of congenital myasthenic syndrome. Meanwhile, he was also involved in university and college governance and contributed widely to the Medical Research Council, government committees, research charities and the Association of British Neurologists. Among many honours, he was elected Fellow of the Royal Society in 1991, appointed Commander of the British Empire in 1996 and made a Foreign Associate Member of the Institute of Medicine of the United States in 2001. Nearing and following retirement from Oxford, where he continued to see patients with myasthenia, he was the President of the Association of British Neurologists and Editor of Brain, and led a National Institutes of Health-funded international trial of thymectomy.
Collapse
Affiliation(s)
- Angela Vincent
- Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, Oxford OX3 9DU, UK.
| |
Collapse
|
7
|
Vincent A. Autoantibodies in neuromuscular transmission disorders. Ann Indian Acad Neurol 2011; 11:140-5. [PMID: 19893659 PMCID: PMC2771981 DOI: 10.4103/0972-2327.42932] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2008] [Accepted: 07/21/2008] [Indexed: 12/20/2022] Open
Abstract
It is a great pleasure to be asked to honour the memory of Dr. Baldev Singh by reviewing the field of autoantibodies in myasthenia gravis and other neurotransmission disorders. The neuromuscular junction (NMJ) is the site of a number of different autoimmune and genetic disorders, and it is also the target of many neurotoxins from venomous snakes, spiders, scorpions and other species. The molecular organization of the NMJ is graphically represented in Figure 1A, where different ion channels, receptors and other proteins are shown. Four of the ion channels or receptors are directly involved in autoimmune diseases. This brief review will not only concentrate on these conditions but also illustrate how their study is helping us to understand the etiology of rare but treatable neurological syndromes of the central nervous system.
Collapse
Affiliation(s)
- Angela Vincent
- Department of Clinical Neurology and Weatherall Institute of Molecular Medicine, University of Oxford, UK
| |
Collapse
|
8
|
Punga AR, Nygren I, Askmark H, Stålberg EV. Monozygous twins with neuromuscular transmission defects at opposite sides of the motor endplate. Acta Neurol Scand 2009; 119:207-11. [PMID: 18684214 DOI: 10.1111/j.1600-0404.2008.01082.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Disorders affecting the postsynaptic side of the neuromuscular junction include autoimmune myasthenia gravis (MG) as well as some of the congenital myasthenic syndromes (CMS). Lambert-Eaton myasthenic syndrome (LEMS) is an acquired autoimmune neuromuscular disorder in which autoantibodies are directed against the presynaptic calcium channels. Here we describe two monozygous twin brothers: case 1 was diagnosed with an indeterminate form of acquired postsynaptic neuromuscular junction defect at age 32 and case 2 with LEMS at age 47. Case 1 presented clinically with mild generalized myasthenic weakness, neurophysiological examination revealed disturbed neuromuscular transmission along with probable myositis and serum analysis regarding antibodies against the acetylcholine receptor and muscle-specific tyrosine kinase was negative. Case 2 presented with proximal muscle fatigue accompanied by areflexia at rest and antibodies against the P/Q-type voltage-gated calcium channels were present. Neurophysiologically, case 2 had reduced baseline compound motor action potential amplitudes on neurography, decrement on low-frequency repetitive nerve stimulation (RNS) and pathological increment on high frequency RNS. To our knowledge this is the first case report of its kind and adds an intriguing contrast to the more common diagnosis of CMS in monozygous twins.
Collapse
Affiliation(s)
- A R Punga
- Department of Clinical Neurophysiology, Uppsala University Hospital, Uppsala, Sweden.
| | | | | | | |
Collapse
|
9
|
Willcox N, Leite MI, Kadota Y, Jones M, Meager A, Subrahmanyam P, Dasgupta B, Morgan BP, Vincent A. Autoimmunizing mechanisms in thymoma and thymus. Ann N Y Acad Sci 2008; 1132:163-73. [PMID: 18567866 DOI: 10.1196/annals.1405.021] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Autoimmunizing mechanisms are very hard to study in humans, so we have focused on vital clues in thymomas and hyperplastic thymuses in myasthenia gravis (MG). According to our multi-step hypothesis: thymic epithelial cells (TEC) present epitopes from the isolated acetylcholine receptor (AChR) subunits they express, and autoimmunize helper T cells; subsequently, these evoke "early antibodies" that then attack rare thymic myoid cells expressing intact AChR; in the resulting germinal centers, autoantibodies diversify to recognize native AChR. We have studied: 1) thymomas, to identify autoimmunizing cell types, focusing on IFN-alpha, against which many patients have high titer autoantibodies, as in another highly informative autoimmune syndrome. Although IFN-alpha is much easier to label than the sparse and delicate AChR subunits, we have not yet located obviously autoimmunizing micro-environments; 2) hyperplastic MG thymuses, where we find (a) upregulation of complement receptors and regulators on hyperplastic TEC and deposition of activated C3b complement component on them, (b) absence of complement regulators from almost all myoid cells, indicating vulnerability to attack, and (c) deposition of C3b, and even of the terminal membrane attack complex, especially on the myoid cells close to the infiltrating germinal centers. The changes are very similar in over 50% of the so-called seronegative patients with generalized MG (SNMG) but without detectable autoantibodies against AChR or MuSK, consistently with other evidence that they belong to the spectrum of AChR-seropositive MG. Together, moreover, our findings implicate both myoid cells and TEC in autoimmunization, and thus strongly support our hypothesis.
Collapse
Affiliation(s)
- Nick Willcox
- Neuroscience Group, Weatherall Institute for Molecular Medicine, University of Oxford, England, UK.
| | | | | | | | | | | | | | | | | |
Collapse
|
10
|
Vincent A, Leite MI, Farrugia ME, Jacob S, Viegas S, Shiraishi H, Benveniste O, Morgan BP, Hilton-Jones D, Newsom-Davis J, Beeson D, Willcox N. Myasthenia gravis seronegative for acetylcholine receptor antibodies. Ann N Y Acad Sci 2008; 1132:84-92. [PMID: 18567857 DOI: 10.1196/annals.1405.020] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Antibodies to muscle-specific kinase (MuSK) are found in a variable proportion of patients with myasthenia without typical acetylcholine receptor (AChR) antibodies, but their characteristics and pathogenic mechanisms are not fully understood. We discuss the incidence and pathogenicity of MuSK antibodies and how clinical studies, animal models, and cultured cell lines can be used to elucidate their pathogenic mechanisms. Patients without either AChR or MuSK antibodies (seronegative myasthenia) appear to present another disease subtype that is highly similar to that of typical myasthenia gravis. We demonstrate a new method that detects AChR antibodies in these patients and show that these low-affinity AChR antibodies are predominantly IgG1 and can activate complement C3b deposition. Similarly MuSK antibodies, although mainly IgG4, are partially IgG1 and can activate C3b deposition. Overall, these results suggest that complement-activation may be an important pathogenic mechanism even in patients without conventional AChR antibodies.
Collapse
Affiliation(s)
- Angela Vincent
- Neurosciences Group, Weatherall Institute of Molecular Medicine and Department of Clinical Neurology, John Radcliffe Hospital, Oxford, United Kingdom.
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
11
|
Leite MI, Jacob S, Viegas S, Cossins J, Clover L, Morgan BP, Beeson D, Willcox N, Vincent A. IgG1 antibodies to acetylcholine receptors in 'seronegative' myasthenia gravis. ACTA ACUST UNITED AC 2008; 131:1940-52. [PMID: 18515870 PMCID: PMC2442426 DOI: 10.1093/brain/awn092] [Citation(s) in RCA: 316] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
Only around 80% of patients with generalized myasthenia gravis (MG) have serum antibodies to acetylcholine receptor [AChR; acetylcholine receptor antibody positive myasthenia gravis (AChR-MG)] by the radioimmunoprecipitation assay used worldwide. Antibodies to muscle specific kinase [MuSK; MuSK antibody positive myasthenia gravis (MuSK-MG)] make up a variable proportion of the remaining 20%. The patients with neither AChR nor MuSK antibodies are often called seronegative (seronegative MG, SNMG). There is accumulating evidence that SNMG patients are similar to AChR-MG in clinical features and thymic pathology. We hypothesized that SNMG patients have low-affinity antibodies to AChR that cannot be detected in solution phase assays, but would be detected by binding to the AChRs on the cell membrane, particularly if they were clustered at the high density that is found at the neuromuscular junction. We expressed recombinant AChR subunits with the clustering protein, rapsyn, in human embryonic kidney cells and tested for binding of antibodies by immunofluorescence. To identify AChRs, we tagged either AChR or rapsyn with enhanced green fluorescence protein, and visualized human antibodies with Alexa Fluor-labelled secondary or tertiary antibodies, or by fluorescence-activated cell sorter (FACS). We correlated the results with the thymic pathology where available. We detected AChR antibodies to rapsyn-clustered AChR in 66% (25/38) of sera previously negative for binding to AChR in solution and confirmed the results with FACS. The antibodies were mainly IgG1 subclass and showed ability to activate complement. In addition, there was a correlation between serum binding to clustered AChR and complement deposition on myoid cells in patients' thymus tissue. A similar approach was used to demonstrate that MuSK antibodies, although mainly IgG4, were partially IgG1 subclass and capable of activating complement when bound to MuSK on the cell surface. These observations throw new light on different forms of MG paving the way for improved diagnosis and management, and the approaches used have applicability to other antibody-mediated conditions.
Collapse
Affiliation(s)
- Maria Isabel Leite
- Neurosciences Group, Weatherall Institute of Molecular Medicine, Department of Clinical Neurology, University of Oxford, Oxford and Department of Medical Biochemistry and Immunology, School of Medicine, Cardiff University, Cardiff, UK
| | - Saiju Jacob
- Neurosciences Group, Weatherall Institute of Molecular Medicine, Department of Clinical Neurology, University of Oxford, Oxford and Department of Medical Biochemistry and Immunology, School of Medicine, Cardiff University, Cardiff, UK
| | - Stuart Viegas
- Neurosciences Group, Weatherall Institute of Molecular Medicine, Department of Clinical Neurology, University of Oxford, Oxford and Department of Medical Biochemistry and Immunology, School of Medicine, Cardiff University, Cardiff, UK
| | - Judy Cossins
- Neurosciences Group, Weatherall Institute of Molecular Medicine, Department of Clinical Neurology, University of Oxford, Oxford and Department of Medical Biochemistry and Immunology, School of Medicine, Cardiff University, Cardiff, UK
| | - Linda Clover
- Neurosciences Group, Weatherall Institute of Molecular Medicine, Department of Clinical Neurology, University of Oxford, Oxford and Department of Medical Biochemistry and Immunology, School of Medicine, Cardiff University, Cardiff, UK
| | - B. Paul Morgan
- Neurosciences Group, Weatherall Institute of Molecular Medicine, Department of Clinical Neurology, University of Oxford, Oxford and Department of Medical Biochemistry and Immunology, School of Medicine, Cardiff University, Cardiff, UK
| | - David Beeson
- Neurosciences Group, Weatherall Institute of Molecular Medicine, Department of Clinical Neurology, University of Oxford, Oxford and Department of Medical Biochemistry and Immunology, School of Medicine, Cardiff University, Cardiff, UK
| | - Nick Willcox
- Neurosciences Group, Weatherall Institute of Molecular Medicine, Department of Clinical Neurology, University of Oxford, Oxford and Department of Medical Biochemistry and Immunology, School of Medicine, Cardiff University, Cardiff, UK
| | - Angela Vincent
- Neurosciences Group, Weatherall Institute of Molecular Medicine, Department of Clinical Neurology, University of Oxford, Oxford and Department of Medical Biochemistry and Immunology, School of Medicine, Cardiff University, Cardiff, UK
| |
Collapse
|
12
|
Vincent A. Autoantibodies in different forms of myasthenia gravis and in the Lambert-Eaton syndrome. HANDBOOK OF CLINICAL NEUROLOGY 2008; 91:213-227. [PMID: 18631844 DOI: 10.1016/s0072-9752(07)01506-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Affiliation(s)
- Angela Vincent
- Department of Clinical Neurology, University of Oxford, Oxford, UK.
| |
Collapse
|
13
|
Leite MI, Jones M, Ströbel P, Marx A, Gold R, Niks E, Verschuuren JJGM, Berrih-Aknin S, Scaravilli F, Canelhas A, Morgan BP, Vincent A, Willcox N. Myasthenia gravis thymus: complement vulnerability of epithelial and myoid cells, complement attack on them, and correlations with autoantibody status. THE AMERICAN JOURNAL OF PATHOLOGY 2007; 171:893-905. [PMID: 17675582 PMCID: PMC1959483 DOI: 10.2353/ajpath.2007.070240] [Citation(s) in RCA: 93] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In early-onset myasthenia gravis, the thymus contains lymph node-type infiltrates with frequent acetylcholine receptor (AChR)-specific germinal centers. Our recent evidence/two-step hypothesis implicates hyperplastic medullary thymic epithelial cells (expressing isolated AChR subunits) in provoking infiltration and thymic myoid cells (with intact AChR) in germinal center formation. To test this, we screened for complement attack in a wide range of typical generalized myasthenia patients. Regardless of the exact serology, thymi with sizeable infiltrates unexpectedly showed patchy up-regulation of both C5a receptor and terminal complement regulator CD59 on hyperplastic epithelial cells. These latter also showed deposits of activated C3b complement component, which appeared even heavier on infiltrating B cells, macrophages, and especially follicular dendritic cells. Myoid cells appeared particularly vulnerable to complement; few expressed the early complement regulators CD55, CD46, or CR1, and none were detectably CD59(+). Indeed, when exposed to infiltrates, and especially to germinal centers, myoid cells frequently labeled for C1q, C3b (25 to 48%), or even the terminal C9, with some showing obvious damage. This early/persistent complement attack on both epithelial and myoid cells strongly supports our hypothesis, especially implicating exposed myoid cells in germinal center formation/autoantibody diversification. Remarkably, the similar changes place many apparent AChR-seronegative patients in the same spectrum as the AChR-seropositive patients.
Collapse
Affiliation(s)
- Maria I Leite
- Department of Clinical Neurology, University of Oxford, Oxford, United Kingdom
| | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
14
|
Fostieri E, Kostelidou K, Poulas K, Tzartos SJ. Recent advances in the understanding and therapy of myasthenia gravis. FUTURE NEUROLOGY 2006. [DOI: 10.2217/14796708.1.6.799] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Myasthenia gravis (MG) is a T-cell dependent autoimmune disease mediated by autoantibodies, which mainly target muscle nicotinic acetylcholine receptors (AChR) and cause loss of functional AChRs in the neuromuscular junction. Both MG and its major autoantigen are studied extensively, yet the etiology of the disease remains unclear, although it is known to be associated with the thymus. A genetic predisposition, combined with several unidentified environmental stimuli, likely creates a favorable milieu in which the disease can appear. Current research focusses on elucidating the cellular and molecular pathways of immune dysregulation, which underly MG outburst and progression. Considerable progress has been made concerning the involvement of the thymus, the identification of impaired mechanisms of immune control and the B–T-cell interaction in MG pathogenesis, while the role of chemokines arises as an intriguing new puzzle. Recent findings fueled the development of novel therapeutic approaches with some encouraging, although preliminary, results. This review summarizes recent achievements in the fields of both basic research and therapeutics.
Collapse
Affiliation(s)
- Efrosini Fostieri
- Hellenic Pasteur Institute, Department of Biochemistry, 127 Vas. Sofias Avenue, 11521 Athens, Greece
| | - Kalliopi Kostelidou
- Hellenic Pasteur Institute, Department of Biochemistry, 127 Vas. Sofias Avenue 11521 Athens, Greece
| | | | - Socrates J Tzartos
- Hellenic Pasteur Institute, Department of Biochemistry, 127 Vas. Sofias Avenue, 11521 Athens, Greece and, Department of Pharmacy, University of Patras, 26504 Patras, Greece
| |
Collapse
|
15
|
Abstract
Ion channels are crucial elements in neuronal signaling and synaptic transmission, and defects in their function are known to underlie rare genetic disorders, including some forms of epilepsy. A second class of channelopathies, characterized by autoantibodies against ligand- and voltage-gated ion channels, cause a variety of defects in peripheral neuromuscular and ganglionic transmission. There is also emerging evidence for autoantibody-mediated mechanisms in subgroups of patients with central nervous system disorders, particularly those involving defects in cognition or sleep and often associated with epilepsy. In all autoimmune channelopathies, the relationship between autoantibody specificity and clinical phenotype is complex. But with this new information, autoimmune channelopathies are detected and treated with increasing success, and future research promises new insights into the mechanisms of dysfunction at neuronal synapses and the determinants of clinical phenotype.
Collapse
Affiliation(s)
- Angela Vincent
- Neurosciences Group, Department of Clinical Neurology, Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, Oxford OX3 9DS, United Kingdom.
| | | | | |
Collapse
|
16
|
Abstract
The neuromuscular junction (NMJ) is a prototype synapse and myasthenia gravis is the prototypic antibody-mediated disorder. There are now three other disorders of neuromuscular transmission caused by antibodies to other essential components of the NMJ. Antibodies to the muscle-specific kinase, MuSK, are defining a new form of myasthenia that can be associated with muscle atrophy. Antibodies to voltage-gated calcium channels are responsible for muscle weakness and autonomic dysfunction in the Lambert Eaton myasthenic syndrome. Antibodies to voltage-gated potassium channels are found in patients with a range of disorders affecting the NMJ, the autonomic system or the central nervous system. The pathogenic mechanisms probably depend on the IgG subclass of the antibodies and are only partly shared between the diseases.
Collapse
Affiliation(s)
- A Vincent
- Neurosciences Group, Department of Clinical Neurology, Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, Oxford, UK.
| |
Collapse
|
17
|
|
18
|
Benveniste O, Jacobson L, Farrugia ME, Clover L, Vincent A. MuSK antibody positive myasthenia gravis plasma modifies MURF-1 expression in C2C12 cultures and mouse muscle in vivo. J Neuroimmunol 2005; 170:41-8. [PMID: 16213598 DOI: 10.1016/j.jneuroim.2005.08.016] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2005] [Accepted: 08/15/2005] [Indexed: 12/18/2022]
Abstract
MG is an antibody-mediated disease that is often treated with corticosteroids. Antibodies to the muscle specific tyrosine kinase (MuSK) have been identified in a proportion of patients with myasthenia gravis (MG) without acetylcholine receptor (AChR) antibodies. MuSK-MG patients often suffer from marked facial muscle weakness, and some patients develop facial and tongue muscle atrophy. MuSK is a receptor tyrosine kinase that plays an essential role during development and is thought to play a trophic role in mature muscle. It is possible, therefore, that the muscle atrophy results from the action of the MuSK antibodies themselves, but effects of corticosteroids on muscle might also be involved. Muscle atrophy in vivo is associated with upregulation of striated Muscle RING-Finger protein-1 (MURF-1), and MURF-1 is also upregulated in C2C12 myotubes exposed to the corticosteroid, dexamethasone (Dex). Here we investigated the effects of MuSK antibodies or Dex on MURF-1 expression in C2C12 cultures and in mouse muscles after treatment in vivo, using quantitative Western blotting. We also looked at expression of neural cell adhesion molecule (NCAM, CD56) that is upregulated after denervation in vivo. MuSK-MG plasma and purified IgG from a patient with marked muscle atrophy modestly increased MURF-1 expression in C2C12 cells in culture, and MURF-1 expression in mouse masseter (facial) muscle, but not in gastrocnemius (leg). Dex had a more marked effect on MURF-1 expression in C2C12 cells, but did not affect MURF-1 expression in either muscle. However, both in C2C12 cells and in vivo, Dex substantially reduced NCAM expression. These results provide the first evidence that MuSK-MG plasma can influence expression of an atrophy-related protein, and preliminary evidence that a facial muscle, the masseter, is more susceptible to this effect. They indicate the need for further studies on muscle atrophy, MuSK-MG antibodies, the effects of steroids, and the intracellular pathways involved.
Collapse
|
19
|
Vincent A, Leite MI. Neuromuscular junction autoimmune disease: muscle specific kinase antibodies and treatments for myasthenia gravis. Curr Opin Neurol 2005; 18:519-25. [PMID: 16155434 DOI: 10.1097/01.wco.0000180660.57801.3f] [Citation(s) in RCA: 116] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
PURPOSE OF REVIEW Some of the 20% of myasthenia gravis patients who do not have antibodies to acetylcholine receptors (AChRs) have antibodies to muscle specific kinase (MuSK), but a full understanding of their frequency, the associated clinical phenotype and the mechanisms of action of the antibodies has not yet been achieved. Moreover, some patients do not respond well to conventional corticosteroid therapy. Here we review recent clinical and experimental studies on MuSK antibody associated myasthenia gravis, and summarize the results of newer treatments for myasthenia gravis. RECENT FINDINGS MuSK antibodies are found in a variable proportion of AChR antibody negative myasthenia gravis patients who are often, but not exclusively, young adult females, with bulbar, neck, or respiratory muscle weakness. The thymus histology is normal or only very mildly abnormal. Surprisingly, limb or intercostal muscle biopsies exhibit no reduction in AChR numbers or complement deposition. However, patients without AChR or MuSK antibodies appear to be similar to those with AChR antibodies and may have low-affinity AChR antibodies. A variety of treatments, often intended to enable corticosteroid doses to be reduced, have been used in all types of myasthenia gravis with some success, but they have not been subjected to randomized clinical trials. SUMMARY MuSK antibodies define a form of myasthenia gravis that can be difficult to diagnose, can be life threatening and may require additional treatments. An improved AChR antibody assay may be helpful in patients without AChR or MuSK antibodies. Clinical trials of drugs in other neuroimmunological diseases may help to guide the treatment of myasthenia gravis.
Collapse
Affiliation(s)
- Angela Vincent
- Neurosciences Group, Weatherall Institute of Molecular Medicine and Department of Clinical Neurology, University of Oxford, Oxford, UK.
| | | |
Collapse
|