眼肌无力的诊断及依据

重症肌无力是乙酰胆碱受体抗体介导的,细胞免疫依赖及补体参与的神经-肌肉接头处（NMJ）传递障碍的自身免疫性疾病。眼肌症状是最为多见的首发症状,表现为上眼睑下垂、复视、斜视等,尤以眼睑下垂最多。通过典型的临床表现及临床实验即可诊断、腾喜龙试验、血清抗体检测、电子诊断可以进一步确诊。     

Antibody-secreting cells to acetylcholine receptor and to presynaptic membrane receptor in seronegative myasthenia gravis

Peripheral blood and bone marrow from seronegative and seropositive myasthenics were evaluated for antibody-secreting cells (ASC). Cells secreting antibody to acetylcholine receptor (AchR) and to presynaptic membrane receptor (prsmR) were counted using an immunospot assay. Immunoglobulin G (IgG) anti-AchR ASC were present in peripheral blood lymphocytes (PBL) from nine of 13 seronegative and nine of 12 seropositive myasthenics and in bone marrow lymphocytes (BML) from nine of 13 seronegative and eight of 12 seropositive myasthenics. The mean number of IgG anti-AchR ASC was lower for seronegative than for seropositive patients (P < 0.01 for PBL and P < 0.0001 for BML). In seropositive patients the mean number of IgG anti-AchR ASC was higher for BML than for PBL (P < 0.01); in seronegative patients it was not. IgG anti-prsmR ASC were detected in PBL from four of eight seronegative and six of eight seropositive myasthenics and in BML from three of eight seronegative and five of eight seropositive patients. The mean number of IgG-anti-prsmR ASC did not differ between seronegative and seropositive patients for PBL but for BML the value was higher for seropositive than for seronegative patients (P < 0.01). We conclude that seronegative myasthenia gravis is an autoimmune disease and that ASC to AchR and to prsmR are present both in the blood and the bone marrow in seronegative patients as in seropositive ones. A major difference between the groups lies in the significantly greater number of ASC found in the bone marrow in the seropositive cohort.     

Antigen presentation and T cell specificity repertoire in determining responsiveness to an epitope important in experimental autoimmune myasthenia gravis

The overall goal of this study was to define, in experimental autoimmune myasthenia gravis (EAMG), immunological differences between helper T cells from two inbred rat strains that explain disease susceptibility on the one hand (in Lewis rats) and disease resistance on the other hand (in Wistar Furth rats). The working hypothesis for these studies was that the T cell compartment in Wistar Furth rats may lack the ability to activate responsiveness by existing B cells that have the potential to produce disease-causing antibodies; this quality may be related to a lack of T cell reactivity toward a determinant(s) associated with the alpha subunit sequence α100–116 of the acetylcholine receptor (AChR) that demonstrates immunodominance in Lewis rats. Results presented below are consistent with the conclusion that there is a deficit in the Wistar Furth (WF) T cell specificity repertoire responsible for unresponsiveness to this important AChR epitope; this deficit exists despite the apparent ability of WF antigen presenting cells to bind and present the α100–116 peptide, and is likely responsible for the inability of Wistar Furth T cells to drive an anti-AChR antibody response with disease-causing potential.     

Thymic involvement in myasthenia gravis : Study by immunofluorescent and immunoperoxidase staining

Changes in the thymus are often encountered in myasthenia gravis (MG), together with neuromuscular pathology. In the present study, the cell population of 28 thymuses from patients with MG were analyzed by immunofluorescent and 49 thymuses by immunoperoxidase techniques. We were able to show the presence of sIg receptor positive, SpA reactive medium and large B lymphocytes of light specific density in the majority of thymuses, and to demonstrate a characteristic pattern of distribution in the gland. PAP analysis showed that the infiltrating B cells appeared in the interlobular septa, then reached the medulla, occasionally the cortex which mostly revealed signs of atrophy. These findings are consistent with an autoimmune reaction occurring against a thymic antigen; such an antigen could be acetylcholine receptor (AchR) of the thymic structures, since anti-AchR antibody or serum from patients with MG will react with 60% thymocytes and some epithelial cells and Hassall's corpuscles.     

Evidence against chronic antigen-specific T lymphocyte activation in myasthenia gravis

Myasthenia gravis (MG) is an antigen-specific autoimmune disease caused by antibodies against acetylcholine receptors (AChR) at the post-synaptic membrane of the neuromuscular junction. Clinical and immunological data imply the involvement of AChR-specific T lymphocytes as helper cells for autoantibody production. Direct data to support this hypothesis, however, remain sparse. In the present study, a large population of MG patients was studied for evidence of peripheral blood T cell activation by several assays. Assays based on non-specific measurements of T cell activation as well as assays of antigen-specific clonal expansion were utilized. Levels of soluble IL-2 receptor in serum were modestly elevated in some patients, suggesting T cell activation. However, peripheral blood cells did not show evidence of IL-2 receptor expression or enhanced reactivity to IL-2 in culture. Clonable T cells selected for hypoxanthine phosphoribosyl transferase (hprt) mutation, another non-antigen-specific marker for T cell activation, were not seen with increased frequency except in patients treated with purine analogs. Antigen-specific T cell activation was measured by proliferation assays using heterologous and autologous sources of AChR. Antigen-restimulated peripheral blood cell cultures were cloned by limiting dilution. The vast majority of patients failed to show convincing evidence of AChR specific T cell activation or clonal expansion; only 2 of 44 patients demonstrated clonable autologous AChR-specific T cells. An alternative hypothesis of T cell involvement in MG is proposed in which T cell activation is discontinuous and predominately directed at antigens other than AChR. © 1996 Wiley-Liss, Inc.     

When is there a full recovery for a myasthenia gravis patient?

Summary A myasthenia gravis (MG) patient who seems to have recovered can later have recurrence of myasthenic signs. Clearly clinical remission does not always correspond to the normalization of all the factors involved in the pathogenesis of the disease. In ten patients who had apparently recovered from MG, electromyographic tests of repetitive supramaximal stimulation were performed and the anti-acetylcholine receptor (anti-AChR) antibody was assessed. In two of the ten patients all these tests were normal, thus showing lack of electromyographic myasthenic fatigability and the absence of circulating anti-AChR antibodies. Our hypothesis is that for these two subjects the risk of a recurrence of MG is lower than for the others.

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Zusammenfassung Ein Patient mit Myasthenia gravis kann auch dann, wenn er sich anscheinend von der Erkrankung vollständig erholt hat, Rückfälle aufweisen. Es ist offensichtlich, daß eine klinische Remission durchaus nicht mit der Normalisierung aller beim Krankheitsprozeß mitwirkenden pathogenetischen Faktoren identisch ist. Bei 10 Patienten, die klinisch scheinbar geheilt waren, wurden elektromyographische Untersuchungen mit repetitiver supramaximaler Reizung ausgeführt sowie die Antiacethylcholinrezeptorenantikörper bestimmt. Zwei der 10 Patienten wiesen normale elektromyographische Befunde und das Fehlen zirkulierender Antiacethylcholinrezeptorenantikörper auf. Die Autoren formulieren die Annahme, daß für diese zwei Individuen das Rückfallrisiko niedriger als bei den anderen ist.

     

Rituximab treatment of myasthenia gravis: A systematic review

Rituximab is a chimeric mouse/human anti‐CD20 monoclonal immunoglobulin. We reviewed the efficacy and safety of rituximab in 169 myasthenia gravis (MG) patients from case reports and series. Antibodies to the acetylcholine receptor (AChR) were present in 59% and muscle‐specific tyrosine kinase (MuSK) in 34%. Modified Myasthenia Gravis Foundation of America postintervention scale of minimal manifestations (MM) or better occurred in 44%, and combined pharmacologic and chronic stable remission in 27% overall; MM or better was achieved in 72% of MuSK MG and 30% of AChR MG (P < 0.001). Posttreatment relapses decreased more in MuSK MG (P = 0.05). Response predictors were MuSK MG, less severe disease, and younger age at treatment. Among a responder subset, 26% of AChR and 82% of MuSK MG patients showed decreased posttreatment antibody titers. Rituximab was generally well tolerated. Detectable serum rituximab and depleted CD20⁺ B‐cells were observed up to 20 and 16 weeks, respectively, after 4 weekly infusions. Muscle Nerve 56 : 185–196, 2017     

Efficacy and safety of different dosages of rituximab for refractory generalized AChR myasthenia gravis: A meta-analysis

BackgroundRituximab (RTX) is a mouse-human chimeric anti-CD20 monoclonal antibody and has been increasingly used for preventing relapses in myasthenia gravis (MG). However, the appropriate dose for maximizing the beneficial effects in refractory MG with acetylcholine receptor (AChR) autoantibody is a long-standing and critical debating question.MethodsWe performed a meta-analysis to evaluate the efficacy and safety of the different doses of RTX in 260 refractory AChR-MG patients.ResultsThe AChR-MG patients were divided into low or routine RTX dose groups. An overall proportion of 77% (p = 0.000) AChR-MG patients demonstrated improved clinical status as indicated by the Myasthenia Gravis Foundation of America post-intervention scale (MGFA-PIS). There were 77.1% patients showed improved clinical status in lower dose of RTX group (p = 0.000) and 76.8% in routine protocol group (p = 0.000). Although we found there was no significant difference in the proportion of AChR-MG patients with improved clinical status or adverse reactions between the two groups, adverse reactions might be lower in the lower dose RTX group.ConclusionMost of refractory MG patients with anti-AChR autoantibody were well responsive and tolerated to RTX treatment. Repeated application of lower dose of RTX was effective and might be more appropriate for refractory AChR-MG patients with potential lower side effects.     

重症肌无力T细胞受体基因重排的检测及其临床意义

目的胸腺病变情况与重症肌无力患者的治疗及预后密切相关，为了能早期诊断胸腺瘤。方法用Ｓｏｕｔｈｅｒｎ杂交，分别以ＴＣＲ－α、β及γ为探针检测了一组重症肌力无力患者Ｔ细胞受体（ＴＣＲ）基因重排。结果６例患者ＤＮＡ经ＥｃｏＲＩ酶切，与ＴＣＲ－α、β探针杂交时有一条异常的重排带。这６例患者已４例经手术证实为胸腺肿瘤。结论ＴＣＲ基因重排可能为早期诊断胸腺瘤提供帮助。     

Modulation of acetylcholine receptor function in TE671 (rhabdomyosarcoma) cells by non-AChR ligands: possible relevance to seronegative myasthenia gravis

The acetylcholine receptor (AChR) is the main target antigen in myasthenia gravis (MG), but about 15% of patients with typical, immunologically mediated MG do not have detectable anti-AChR antibodies. Previous studies showed that plasma from these ‘seronegative’ patients (SNMG) reduced AChR function in the human AChR-expressing TE671 cell line, and it was proposed that SNMG plasmas may act indirectly via phosphorylation of AChR. We show here that substances such as the β₂-adrenergic agonist, salbutamol, calcitonin-gene-related-peptide (CGRP), and cholera toxin, that increase intracellular cAMP via binding to specific cell-surface receptors, reduced AChR function in TE671 cells. Moreover, non-specific activation of cell surface proteins by lectins achieved similar results. These observations lead us to hypothesise that SNMG immunoglobulins act in TE671 cells by cross-linking of specific cell surface antigen(s) resulting in generation of intracellular cAMP and/or other second messengers. The role of such antibodies at the neuromuscular junction in vivo could be reduction in AChR function by desensitization and/or damage to the postsynaptic membrane following complement activation.     

Lymphocyte populations in patients with myasthenia gravis. Influence of thymectomy and immunosuppressive drugs

The T/B peripheral blood lymphocyte ratio was evaluated in 51 patients with myasthenia gravis by means of the rosette test and HTLA. Total T cells and T and T.This work was supported by Consiglio Nazionale delle Ricerche, Rome (Contratto n. 80-00537.04)     

Morphological effects of myasthenia gravis patient sera on human muscle cells

Myasthenia gravis (MG) is caused primarily by autoantibodies against the nicotinic acetylcholine receptor (AChR), but autoantibodies to other muscle proteins may be present. Many of these proteins have structural or signalling functions, the disruption of which may affect muscle cell morphology or viability. In order to investigate the role of such autoantibodies in MG, we examined the effect of MG patient sera, of different autoantibody composition and obtained at different stages of disease severity, on primary human muscle cells. Sera from MG patients induced changes in cell morphology from typical elongated cells to an irregular phenotype, caused the formation of inclusion bodies and intracellular vesicles, and led to a disordered arrangement of actin microfilaments. Sera from the most severely affected patients also induced cell death, which did not occur via classic apoptosis. The effects were not complement-mediated and were dose- and time-dependent. As the effects observed in the cell culture system correlated with disease severity, a greater understanding of the individual factors responsible for these effects may improve our understanding of MG pathogenesis and be of value in the assessment of disease in individual patients.     

Antibodies in sera from patients with myasthenia gravis do not bind to nicotinic acetylcholine receptors from human brain

Nicotinic acetylcholine receptors (AChRs) from brains of chickens and rats have recently been purified and characterized (Whiting and Lindstrom, Biochemistry, 25 (1986) 2082-2093; J. Neurosci., 6 (1986) 3061-3069; Proc. Natl. Acad. Sci. U.S.A., 84 (1987) 595-599). Using both antisera and monoclonal antibodies prepared to AChRs from rat brain, we have demonstrated the existence of a homologous AChR in human brain. Here we report that antibodies to muscle AChRs in the sera of patients with myasthenia gravis (MG) do not bind to AChRs from human brain. Similarly, there was no binding of sera from patients with Guillain-Barré, amyotrophic lateral sclerosis, multiple sclerosis, or Lambert-Eaton myasthenic syndrome. Additionally, no binding of any of these sera to the alpha-bungarotoxin (alpha-Bgt) binding protein from human brain could be detected. This data is consistent with other data using antibodies to AChRs from muscle and nerve in demonstrating that the AChR in brain is antigenically distinct from the AChR in skeletal muscle AChR, and, together with the lack of central neurological symptoms in MG, suggests that the low concentrations of anti-AChR antibodies in the cerebrospinal fluid of MG patients do not bind to AChRs in brain.     

Plasma from myasthenia gravis patients reduces acetylcholine receptor agonist-induced Na flux into TE671 cell line

Plasma from myasthenia gravis patients was tested for its ability to inhibit agonist-induced 22Na+ influx into the TE671 cell line that expresses human acetylcholine receptors. Reduced 22Na+ influx correlated weakly with the total anti-acetylcholine receptor antibody level in the plasma, and was also related to the presence of antibody directed against the agonist binding site, as detected by inhibition of 125I-alpha-bungarotoxin binding. However, in some cases there was inhibition of 22Na+ flux without evident anti-alpha-bungarotoxin binding site antibody. We conclude that in most patients antibodies that interfere with 22Na+ influx do so by blocking the agonist binding site. However, in some cases antibodies may be directed at the Na+ ion channel or some important functional determinant.     

Antibodies not directed against the acetylcholine receptor in myasthenia gravis: An immunoblot study

Sera of 45 patients with myasthenia gravis (MG) and of 30 healthy controls were screened for antibodies against muscle antigens in an immunoblotting solid-phase assay using a preparation of human amputated muscle as the substrate. In each group, the sera showed several bands on the blots. The findings are thought to indicate that antibodies against muscle components are normally present in human sera. Sera from patients or controls could be distinguished by differences in the band staining patterns. It is suggested that antibodies which are not directed against the acetylcholine receptor may nonetheless play an important role in the pathogenesis and clinical course of myasthenia gravis.     

重症肌无力患者外周血AIRE、Tfh细胞和Tfr细胞与病情严重性相关分析

目的探讨自身免疫性调节因子(AIRE)、滤泡辅助性T(Tfh)细胞和滤泡调节性T(Tfr)细胞与重症肌无力(MG)患者病情严重程度的相关性。方法收集2015-12—2016-4第四军医大学唐都医院收治的MG患者22例,根据临床表现分为全身型MG(GMG)和眼肌型MG(OMG);同期选取健康体检中心查体者10名作为健康对照。收集MG患者详细临床资料,包括美国MG协会(MGFA)分型及定量MG(QMG)评分。通过流式细胞术分析AIRE阳性细胞比例及Tfh/Tfr比值。结果 (1)AIRE表达在各组间比较差异具有统计学意义(P0.01)。GMG组和OMG组AIRE表达均较对照组降低(P0.01,P0.05),而GMG组与OMG组间比较差异无统计学意义(P0.05)。(2)Tfh/Tfr比值在各组间比较差异具有统计学意义(P0.01)。GMG组和OMG组Tfh/Tfr比值均高于对照组(P0.01,P0.05),且GMG组高于OMG组(P0.05)。(3)MG患者AIRE表达与MGFA分型及QMG评分呈负相关(r=-0.517,P0.05;r=-0.616,P0.01),Tfh/Tfr比值与MGFA分型和QMG评分呈正相关(r=0.761,r=0.581,均P0.01)。结论 AIRE、Tfh/Tfr比值与MG的病情严重程度有一定的相关性,并可能参与了MG的发病。     

Acetylcholinesterase activity of skeletal muscle in a non-immunogenic model for myasthenia gravis in rats

Summary. Myasthenia gravis is caused by an autoimmune attack to acetylcholine receptors of skeletal muscle. Acetylcholine release from motor nerve terminals is upregulated in patients with myasthenia gravis and also in rat "myasthenic" models, dependent on the reduction of the number of acetylcholine receptors. This study addresses the question as to whether at "myasthenic" endplates there are changes in the activity of acetylcholinesterase. To this end we studied acetylcholinesterase activity in junctional and extrajunctional regions of dilator naris, extensor digitorum longus, and hemidiaphragm muscles from rats with α-bungarotoxin-induced myasth-enia gravis. In all studied muscles from "myasthenic" rats there was no significant change of junctional acetylcholinesterase activity. In contrast, in dilator naris and extensor digitorum longus muscles, there was a 60% and 30% increase of extrajunctional acetylcholinesterase activity. There was no significant change in the extrajunctional activity in hemidiaphragm muscles. Velocity sedimentation analysis revealed that the increase in extrajunctional activity in extensor digitorum longus muscles could be attributed to an increase of the activity of the G₄ form of acetylcholinesterase. Treatment of rats with 6.4 μg h⁻¹ neostigmine bromide for 29 days had no influence on junctional and extrajunctional acetylcholinesterase activity of extensor digitorum longus muscles from rats with α-bungarotoxin-induced myasthenia gravis. Received August 26, 1998; accepted November 30, 1998     

Anti-acetylcholine receptor (AChR) antibodies measurement in myasthenia gravis: The use of cell line TE671 as a source of AChR antigen

Acetylcholine receptor (AChR) from the human rhabdomyosarcoma cell line TE671 was compared with that of human ischaemic muscle AChR as a source of the antigen for the diagnosis of myasthenia gravis (MG). The sera, which were anti-TE671 3ell AChR antibody-negative, all came from patients with low anti-human muscle AChR antibody titers. None of the sera that were seronegative as a result of the human muscle AChR RIA became positive with TE671 cell AChR. The overall sensitivity was 7% less using TE671 cell AChR. The lower sensitivity was observed irrespective of the clinical form of MG. It also appeared from this study that epitopes specific to the junctional isoform of human AChR are essential for the detection of low antibody titers, which accounts for this feature, since TE671 cells only express the extrajunctional isoform of AChR in the surface membrane. Accordingly, AChR from cell line TE671 cannot replace human muscle AChR in the conventional diagnostic immunoprecipitation RIA. There are, however, many other useful implications of AChR from cell line TE671.     

Subsets of lymphoid cells in blood and thymus in myasthenia gravis : Monoclonal Antibody Analysis

Lymphoid cell subpopulations in peripheral blood and thymus were analyzed in patients with myasthenia gravis (MG) using monoclonal antibodies. The proportion of lymphocytes of T lineage (OKT 3 +, OKT 4 +, OKT 8 + cells) in peripheral blood of 11 MG patients, was significantly decreased in comparison with controls, but the ratio of OKT 4+/OKT 8+ cells was not different. Thymus cells were studied in 9 patients. The percentage of OKIa 1 + cells was significantly higher in MG thymus than in control thymus (P < 0.0005). There were no significant differences in the proportions of T lymphocyte subsets between MG and control thymuses.