重症肌无力患者血清抗Titin抗体检测的临床意义

目的探讨重症肌无力(myasthenia gravis,MG)患者血清抗Titin抗体检测的临床意义。方法用重组体MGT-30(提纯的Titin片断)作为抗原,应用ELISA对77例MG患者(包括25例胸腺瘤患者)、58例其他神经系统疾病患者及46例健康对照者进行血清抗Titin抗体检测。结果MG、MG合并胸腺瘤和年龄超过40岁而无胸腺瘤的晚发型MG患者组中抗Titin抗体的阳性率分别为63.6%、80%和70.6%,而其他神经系统疾病组和健康对照者中抗Titin抗体阳性者较少,分别为15.5%、6.5%。MG患者组的阳性率明显高于对照组。结论血清抗Titin抗体检测可作为MG诊断的参考指标,尤其对合并胸腺瘤患者可能更具有临床意义。     

Mature, long-lived CD4+ and CD8+ T cells are generated by the thymoma in myasthenia gravis.

Antibodies to muscle acetylcholine receptors, to other muscle antigens, and to some cytokines are found in the majority of patients with thymic tumors (thymomas) and myasthenia gravis (MG). The role of the tumor in initiating autoimmunity, however, is unclear; in particular, it is not known whether the thymoma exports mature and long-lived T cells, which could provide help for antibody production in the periphery. Here, we quantified recently exported thymic T cells using the approach of measuring episomal DNA fragments [T-cell receptor excision circles (TRECs)], generated by T-cell receptor gene rearrangement. Compared to values in healthy individuals (n = 10) or in patients with late-onset MG (n = 8), TREC levels were significantly raised in both the CD4+ and CD8+ peripheral blood compartments of patients with thymoma and MG (n = 14, p = 0.002 and p = 0.0004 compared to healthy controls) but only in the CD8+ compartment of the three patients with thymoma without MG (p = 0.4 and p = 0.01 for CD4+ and CD8+). TREC levels decreased following thymectomy to values similar to controls but were substantially raised in patients who had developed tumor recurrence (n = 6, p = 0.04 and p = 0.02 for CD4+ and CD8+); this was associated with increased antibodies to interferon-alpha and interleukin-12 in the one case studied serially. Collectively, these results support the hypothesis that the neoplastic thymoma tissue itself can generate and export mature, long-lived T cells and that these T cells reflect the thymic pathology and are likely to be related to the associated autoimmune diseases. The results also provide a new approach for early diagnosis of thymoma recurrence.     

Detection of antibody classes and subpopulations in Myasthenia gravis patients using a new nonradioactive enzyme immunoassay

To investigate the presence of antibodies in myasthenia gravis (MG) patients, we have developed a new reproducible and sensitive enzyme immunoassay (EIA-AChR), in which a β subunit-specific monoclonal antibody (mAb 73) immobilizes fetal calf acetylcholine receptors (AChRs). We tested 92 MG patients (42 with positive and 50 with negative antibody titers), 60 healthy controls, and 40 controls with other autoimmune diseases. EIA-AChR detected immunoglobulin G (IgG) titers in all of the seropositive samples, with a significant correlation between these and those obtained using the traditional immunoprecipitation method. Moreover, 5 seronegative patients at immunoprecipitation assay were positive at EIA-AChR. EIA-AChR was also useful in revealing: (1) a seropositive patient subpopulation with generalized MG who had Abs directed against α-Bungarotoxin binding sites; and (2) patients with IgM directed against fetal calf AChR (detected in 13 seronegative and 16 seropositive MG patients, and in 6 of the patients with other autoimmune diseases). © 1997 John Wiley & Sons, Inc. Muscle Nerve 20: 800–808, 1997     

High frequency of allergic conjunctivitis in myasthenia gravis without thymoma

OBJECTIVES: To investigate the frequency of allergic disorders in myasthenia gravis (MG) patients and characterize the features of MG associated with allergic disorders. METHODS: Frequencies of past and present common allergic disorders in 160 MG patients who visited the Department of Neurology, Kyushu University Hospital from April 2000 to July 2003 and in 81 neurological normal controls were studied. RESULTS: Among various allergic disorders, the frequency of allergic conjunctivitis (AC) was significantly higher in MG patients (39/160, 24.4%, p(corr)=0.0112), especially with MG without thymoma (36/123, 29.3%, p(corr)=0.0016), in comparison to the controls (6/81, 7.4%). MG patients with AC showed a significantly higher rate of seronegative MG (43.6% vs. 17.4%, p=0.008) and a higher tendency of ocular MG (43.6% vs. 28.1%, p=0.071). Moreover, MG with AC had significantly lower anti-acetylcholine receptor antibody titers (median 6.8 nmol/l vs. median 23.6 nmol/l, p=0.0359) as well as a lower rate of coexisting thymoma (7.7% vs. 17.4%, p=0.016). The incidence of myasthenic crisis was also lower in MG with AC than without AC, yet the difference was not significant (7.7% vs. 15.7%). CONCLUSION: There was a significant association of AC with MG especially for ocular or seronegative MG in cases without thymoma.     

血清乙酰胆碱受体抗体、突触前膜抗体和胸腺瘤相关抗体与重症肌无力发病关系的研究

本研究用ＥＬＩＳＡ法同步、动态地检测了２８５例ＭＧ患者血清乙酰胆碱受体抗体（ＡｃｈＲａｂ）、突触前膜抗体（ＰｓＭａｂ）和胸腺瘤相关抗体（ＣＡＥａｂ）的变化。实验结果表明，ＭＧ患者体内增高的ＡｃｈＲａｂ是ＭＧ发病的主要体液因素。部分血清ＡｃｈＲａｂ阴性ＭＧ患者（１７．５％）的发病，可能与血清ＰｓＭａｂ异常有关。另一部分血清ＡｃｈＲａｂ和ＰｓＭａｂ均异常的ＭＧ患者（１２．６％），则可能同时存在骨骼肌神经肌接头突触前和突触后的损害。血清ＣＡＥａｂ测定在辅助诊断胸腺瘤方面具有高度的灵敏度和特异性，可作为临床早期诊断胸腺瘤的过筛检查。     

Myasthenia gravis muscle antibodies examined by ELISA: IgG and IgM antibodies characterize different patient subgroups

Sera from 90 myasthenia gravis (MG) patients were examined for antibodies against skeletal muscle citric acid extract (CA) antigens by ELISA and indirect haemagglutination (IHA). 31% (ELISA) and 24% (IHA) of the sera were positive, and the results of the two tests were in good agreement. 18 of 28 patients positive in ELISA had IgG CA-antibodies, 10 had IgM and 3 IgA CA-antibodies. The patients with IgG antibodies had a high mean age of MG disease onset, and 9/14 thymectomized patients had a thymoma. Patients with IgM CA-antibodies had a much lower age of onset and 4/5 thymectomized patients had thymus hyperplasia. IgM antibody positive patients had a long disease duration, indicating that they produce IgM antibodies for an indefinite period of time without switching to IgG antibody production.     

Novel autoantibodies to a voltage-gated potassium channel Kv1.4 in a severe form of myasthenia gravis

Sera from patients with myasthenia gravis (MG) were screened for autoantibodies to skeletal muscle-specific antigens by immunoprecipitation assay, using rhabdomyosarcoma and leukemia cell lines. Eleven of 61 MG sera immunoprecipitated a rhabdomyosarcoma-specific 70-kDa protein, which was identified as the voltage-gated K+ channel 1.4 (Kv1.4). This antibody specificity was not detected in 30 patients with polymyositis/dermatomyositis, 9 with thymoma alone, or 30 healthy controls. Clinical features associated with anti-Kv1.4 antibody included bulbar involvement, myasthenic crisis, thymoma, myocarditis, and QT prolongation on electrocardiogram. These findings suggest that anti-Kv1.4 antibody is a novel autoantibody associated with a severe MG subset and thymoma.     

重症肌无力病人胸腺切除术后血清自身抗体水平变化和临床转归分析

６９例重症肌无力（ＭＧ）病人行胸腺切除术，术前血清乙酰胆碱受体抗体水平均高于正常，术后半年抗体水平明显下降，胸腺增生组（２０例）尤为显著．胸腺瘤组（４９例）术前胸腺瘤相关抗体水平增高，但术后半年内无明显变化．６９例ＭＧ患者胸腺切除术后４年，症状总缓解率为７６．８１％，其中胸腺增生组９５％，胸腺瘤组６９．３９％。作者认为，对于伴有胸腺增生或胸腺瘤的ＭＧ患者，胸腺切除术是有效的，应该列为治疗的第一选择。     

重症肌无力免疫病原学研究Ⅰ重症肌无力患者血清免疫学研究

本文用ＥＬＩＳＡ法同步、动态地观测了２８５例ＭＧ患者血清ＡｃｈＲａｂ、ＰｓＭａｂ和ＣＡＥａｂ的变化。实验结果表明ＭＧ患者体内增高的ＡｃｈＲａｂ是ＭＧ发病的主要体液因素。部分血清ＡｃｈＲａｂ阴性ＭＧ患者（１７．５％）的发病可能与血清ＰｓＭａｂ异常有关。另一部分血清ＡｃｈＲａｂ和ＰｓＭａｂ均异常的ＭＧ患者（１２．６％）则可能同时存在骨骼肌神经肌肉接头突触前和突触后的损害。血清ＣＡＥａｂ测定在辅助诊断胸腺瘤方面具有高度的灵敏度和特异性，可作为临床早期诊断胸腺瘤的过筛检查。     

TNFA and TNFB polymorphisms in myasthenia gravis

BACKGROUND: Tumor necrosis factor (TNF) alpha and TNF-beta are proinflammatory cytokines thought to be involved in the pathogenesis of myasthenia gravis (MG). OBJECTIVE: To examine whether TNF polymorphisms are associated with MG, MG subgroups, and the presence of titin and ryanodine-receptor antibodies. PATIENTS AND METHODS: We did genotyping on 30 patients with MG and 92 healthy blood donors for 2 biallelic TNFA polymorphisms (G to A at positions -238 and -308) and 1 TNFB polymorphism (NcoI digestive site) using methods based on the polymerase chain reaction. RESULTS: Patients with thymoma were typically homozygous for both the TNFA*T1 and the TNFB*2 alleles, but patients having an early onset of MG without thymoma were carriers of the TNFA*T2 and TNFB*1 alleles. Patients without thymoma who had the titin antibody had the same high frequency of TNFA*T1 and TNFB*2 as patients with thymoma, whereas patients without the titin antibody carried the same allele, TNFA*T2 and TNFB*1, regardless of age and thymic disease. No association was found with acetylcholine-receptor levels or disease severity for any of the TNFA or TNFB polymorphisms. CONCLUSION: Patients having MG, including those with thymoma, who have the titin antibody are most often homozygous for the TNFA*T1 and TNFB*2 alleles, whereas the presence of the TNFA*T2 and TNFB*1 alleles correlates with early-onset MG and the absence of titin antibodies.     

Anti-AChR antibodies, thymic histology, and T cell subsets in myasthenia gravis

The relationship between the titers of antibody against acetylcholine receptor (AChR) and T helper/suppressor balance (assessed by the OKT4/OKT8 ratio) were investigated in 74 patients with myasthenia gravis (MG). All patients with elevated AChR antibody titers (greater than 100 nM) had hyperplastic thymuses, while most patients with low or negative antibody titers (less than 1 nM) had involuted thymuses. All patients with thymoma had positive, though not very high, antibody titers. No correlation was found between anti-AChR antibody levels and OKT4/OKT8 ratios except for patients with thymoma. Thus, it appears that AChR antibody titers are more closely related to thymic pathology than to peripheral T cell imbalance. These results are consistent with the hypothesis giving a central role to thymic lymphocytes in the AChR antibody production, either as antibody producer B cells or helper T cells.     

High anti-EBNA-1 IgG levels are associated with early-onset myasthenia gravis

Background: Myasthenia gravis (MG) is an autoimmune disorder mediated by antibodies against the acethylcholine receptor (AchR) of the neuromuscular junction in the majority of patients. Methods: Here, we examined IgG antibodies against the type 1 nuclear antigen of Epstein‐Barr virus (EBNA‐1) in the sera of 158 patients with MG compared to 184 healthy controls. Results: Although serum concentration in the sera was not different, high anti‐EBNA‐1 IgG titers (above 90th percentile of the normal values) were more common in the patients (26.6 vs. 16.3%, P = 0.024). In addition, high EBNA‐1 IgG levels occurred more frequently amongst the 94 patients with early‐onset myasthenia gravis (EOMG, 30.8%) as compared to the 64 patients with late‐onset disease (LOMG, 14.1%) (P = 0.021). Using multiple logistic regression, high serum concentration of the anti‐EBNA‐1 IgG antibodies was significantly associated with EOMG (OR: 3.17, P = 0.027), even after adjustment for sex, presence/absence of anti‐AchR antibodies and presence/absence of anti‐Titin antibodies. Out of 39 patients with EOMG, who underwent thymectomy, 18 patients (46%) had thymoma, 6 had thymic hyperplasia (15%), and 15 patients had thymic atrophy (39%); there was no difference comparing EBNA‐1 antibody titers in the sera. As no correlation was found between the titers of anti‐AchR, anti‐Titin, and EBNA‐1 antibodies, a dysregulated heterogeneous B‐cell response was unlikely to be responsible for the elevated levels of EBV‐associated antibody in patients. Conclusions: In summary, our data suggest that high levels of EBNA‐1 antibodies are more common in MG compared to healthy controls and are especially associated with EOMG.     

Myasthenia gravis appearing after thymectomy

We aimed to evaluate the clinical characteristics of patients with postoperative myasthenia gravis (MG). We retrospectively studied the data of 174 thymoma patients treated between 1990 and 2008 in Xiangya Hospital. Six of 125 patients without preoperative MG (4.8%) developed postoperative MG. The anti-acetylcholine-receptor binding antibody (ARAb) titers were elevated preoperatively in 22 of the 125 patients (17.6%) who did not have preoperative MG (range, 0.5-67.6 nmol/L). Four of six patients with postoperative MG had positive ARAb levels preoperatively. Serum titers were exacerbated in all six patients at the onset of postoperative MG. Postoperative MG was responsive to anti-cholinesterase compounds and/or steroids. We concluded that a thymectomy did not prevent postoperative MG. Exacerbated ARAb levels after thymectomy suggested an extrathymic production of ARAb. We suggest that a rise in the ARAb titer might be a risk indictor for post-thymectomy MG.     

重症肌无力患者血清Titin抗体和AchR抗体检测的意义

目的 探讨重症肌无力(MG)患者血清Titin抗体及乙酰胆碱受体(AchR)抗体的检测意义.方法 采用酶联免疫吸附试验(ELISA)对81例MG患者和80例对照组成员进行Titin和AchR抗体的检测.结果 Titin抗体对MG具有特异性,它在合并胸腺瘤的MG(MGT)、晚发型MG患者中有较高的阳性率(分别为80%、69.4%)和抗体水平,明显高于早发型MG患者的阳性率(25%)和抗体水平,差异均有统计学意义(P<0.05).而早发型MG患者中AchR抗体阳性率比晚发型MG患者明显增高.并且早发型MG患者的AchR抗体水平也明显高于晚发型MG和MGT患者,差异均有统计学意义(P<0.05).结论 两种抗体检测为MG诊断和病因学研究提供了重要证据,联合检测可以提高MG诊断的灵敏度.     

Effect of myasthenic IgG on degradation of junctional acetylcholine receptor

We investigated the effect of the lgG from patients with myasthenia gravis (MG) on the degradation of normal rat junctional acetylcholine receptor (AChR) labeled with ¹²⁵l-α-bungarotoxin (BuTx) and calculated the degradation rate (DR). The DR for the lgG from these patients was significantly higher than that from healthy volunteers and patients with other autoimmune diseases. For MG, DR was significantly correlated with the severity of the disease but not with anti-AChR antibody titer. DR was accelerated by lgG from patients with generalized MG whose antibody titers were in the normal range and by lgG from patients with ocular MG. These results indicate that measurement of the DR of junctional AChR in normal rats is more closely correlated with the severity of the disease than is measurement of anti-AChR antibody and that the former is a sensitive and confirmatory method for evaluating MG. © 1993 John Wiley & Sons, Inc.     

Do titin and cytokine antibodies in MG patients predict thymoma or thymoma recurrence?

BACKGROUND: Patients with MG often have other autoantibodies in addition to those against the acetylcholine receptor (AChR). It has been suggested that antibodies to the muscle protein titin may be diagnostic of a thymoma, but they have also been found in patients with late-onset MG. Antibodies to certain cytokines have also been detected in patients with MG and thymoma, and it is not clear whether these antibodies could be more useful clinically. The authors measured antibodies against titin and the cytokines interferon alpha (IFNalpha) and interleukin 12 (IL12) in patients with MG and thymoma or thymoma recurrence, and in patients with MG but without thymoma presenting before (early-onset MG) or after (late-onset MG) 40 years of age. METHOD: Levels of titin, IFNalpha, and IL12 antibodies were determined by radioimmunoassay in 191 patients with MG and 82 controls. RESULTS: As previously reported, titin antibodies were uncommon in patients with early-onset MG. However, in patients with late-onset MG, titin antibodies had similar prevalence and levels to those in patients with MG and thymoma, although the antibodies were uncommon in patients between 40 and 60 years of age presenting without a tumor. By contrast, cytokine antibodies were more common in patients with thymoma than in patients without thymoma, and cytokine antibodies typically increased substantially if the thymoma recurred. CONCLUSIONS: Measurement of titin antibodies has limited use in predicting the presence of a tumor, unless the patient is less than 60 years of age, but measurement of IFNalpha and IL12 antibodies may be helpful in identifying patients with a thymoma recurrence, particularly when mediastinal imaging is equivocal.     

Late onset myasthenia gravis

Late onset myasthenia gravis (MG) is defined as the onset of the disease after the age of 50 in a patient with no clinical or paraclinical evidence of a thymoma. Myasthenia gravis has a bimodal appearance for both sexes with a peak age of onset located in the early onset group and another peak for late onset of MG. Early onset of MG in men is approximately 10 years later than in females. In late onset MG, the thymus is smaller than in early onset and much of the lymphoid tissue has been substituted with fat. There is no morphological evidence that the thymus atrophy seen in late onset MG is any different from the thymus involution which is age-related. The AChR antibody concentration is lower in cases with late onset MG than it is in early onset and in thymoma-associated MG. Sera from late onset MG patients can be divided in 2 groups; those with and those without striated muscle (MGT 30) antibodies. Their presence is not an effect of age since they are not detected among old healthy individuals. Nor is it an effect of long MG duration, since there is no relation between titre and duration. Non-thymoma MG patients who demonstrate an immune response to titin identical to that observed in thymoma, have a worse prognosis and seem to do less well after thymectomy than late onset MG patients without muscle antiboides.     

Serum antibodies to cytomegalovirus in myasthenia gravis: effects of thymectomy and steroids.

The etiology of the immunologic abnormalities in myasthenia gravis (MG) remains unknown. Evidence for persistent viral infection was sought by determining serum antibody titers to several enveloped RNA and DNA viruses. Compared to healthy controls matched for age, sex, geography and socioeconomic status, patients with MG were more likely to have elevated titers of complement-fixing antibody to cytomegalovirus (CMV). Patients with MG not treated with thymectomy or steroids had elevated CMV titers, whereas thymectomized or steroid-treated patients did not; the differences were statistically significant (p less than 0.01). These results are consistent with the hypothesis that there is persistent viral antigenic stimulation in the myasthenic thymus, arising from viral protein incorporation into epithelioid-myoid cell surface membranes and subsequent induction of an antibody to these acetylcholine receptor (AChR)-bearing thymic cells. This antibody then cross-reacts with AChR at the neuromuscular junction.     

Anti-titin antibodies in myasthenia gravis: tight association with thymoma and heterogeneity of nonthymoma patients

BACKGROUND: Titin is the major autoantigen recognized by anti-striated muscle antibodies, which are characteristic of generalized myasthenia gravis (MG). OBJECTIVE: To seek a correlation between anti-titin antibodies and other features of MG patients, including histopathology, age at diagnosis, anti-acetylcholine receptor (anti-AChR), autoantibody titers, and clinical severity. METHODS: A novel, highly specific radioligand assay was performed on a large group of 398 patients with generalized MG. RESULTS: Among thymectomized patients, anti-titin antibodies were present in most patients with thymoma (56/70 [80%]), contrasting with only a minority of patients with thymus atrophy or hyperplasia (17/165 [10%]). They were also present in 64 (41%) of 155 nonthymectomized patients who had a radiologically normal thymus. In these patients and in those who had a histologically normal thymus, anti-titin antibodies were associated with a later age at onset of disease and with intermediate titers of anti-AChR antibodies. After controlling for these 2 variables, disease severity was not significantly influenced by anti-titin antibodies. CONCLUSIONS: Anti-titin antibodies are a sensitive marker of thymoma associated with MG in patients 60 years and younger, justifying the insistent search for a thymoma in MG patients of this age group who have these antibodies. In nonthymoma patients, anti-titin antibodies represent an interesting marker complementary to the anti-AChR antibody titer, identifying a restricted subset of patients. These clinical correlations should prompt further studies to examine the mechanisms leading to the production of anti-titin antibodies.     

B‐cell–activating factor is elevated in serum of patients with myasthenia gravis

Introduction: Myasthenia gravis (MG) is a B‐cell–mediated autoimmune disease. B‐cell–activating factor (BAFF) is a major factor in B‐cell development and activation. In this study we investigated serum BAFF levels in MG patients. Methods: We compared the serum BAFF levels of 20 MG patients with gender‐matched healthy controls. We assayed serum concentrations of BAFF and anti‐acetylcholine receptor antibody (AChR) titers. Results: Serum BAFF levels of MG patients with AChR antibodies were significantly higher than those of healthy controls. A significant positive correlation was observed between serum BAFF levels and anti‐AChR antibody titers. BAFF values did not correlate with disease severity. Conclusions: BAFF may play a major role in the pathogenesis of MG, and it may provide a potential target for therapy in patients with MG. Muscle Nerve 54 : 1030–1033, 2016