The significance of titin antibodies in myasthenia gravis

Myasthenia gravis (MG) is caused by autoantibodies to acetylcholine receptors (AChR). Non-AChR muscle autoantibodies, such as titin antibodies, are present in sera of many MG patients. To study the correlation between titin antibodies and the features of MG, the cDNA segment encoding MGT-30 was amplified and sequenced. The cloned MGT-30 cDNA was expressed in vector pET-30a, and then transfected into E.coli. BL21. We examined titin antibodies in sera of 265 normal subjects, 154 MG patients with different thymic pathology and 48 patients with other neurological diseases. Titin antibodies occurred more frequently in MGT, especially in MG with epithelial predominant-thymoma, and were correlated with the severity of disease. The levels of titin antibodies were reduced 6 months after thymectomy. The specificity of titin antibodies for the detection of thymoma was higher than that of CT examination in MG with thymoma. These results suggest that titin antibodies could be useful in both diagnosis and follow-up of MG patients with thymoma.     

Anti-neuroblastoma antibodies in myasthenia gravis: clinical and immunological correlations

Forty-four of 109 myasthenia gravis (MG) patients (40%) had serum antibodies against human neuroblastoma cells (NBL). Anti-NBL antibodies were most frequent in the sera of MG patients who had either a hyperplastic thymus or a thymoma, clinically mild to moderately severe generalized MG, and a long disease duration (greater than or equal to 11 years). No correlation between individual anti-NBL antibody and anti-acetylcholine receptor (AChR) antibody titers was observed. Seven of the 19 patients negative for anti-AChR antibodies (37%) had anti-NBL antibodies in their sera. These findings provide further evidence for immunological heterogeneity in MG. In addition to the typical autoantibodies to the AChR, autoimmunization against neural antigens can frequently be detected in these patients.     

重症肌无力患者血清titin抗体和乙酰胆碱受体抗体与疾病临床特征的关系

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)抗体与疾病临床特征的关系。方法采用酶联免疫吸附试验对90例MG患者和30例对照组成员进行titin抗体和AChR抗体的检测并进行比较。结果 MG患者AChR抗体、Titin抗体阳性率(76.7%,54.5%)明显高于对照组(10%,6.7%)(χ2=41.667,P=0.000;χ2=21.017,P=0.000)。titin抗体与AChR抗体检测MG的灵敏度分别为54.5%和76.7%,两种抗体并联试验灵敏度为89.4%。titin抗体在伴胸腺病变及晚发型MG患者中有较高阳性率,分别为80.0%和72.5%,明显高于非胸腺瘤组(47.1%,χ2=6.771,P=0.009)和早发型MG患者(40%,χ2=9.46,P=0.002)。全身型MG患者titin抗体与AChR抗体阳性率(69.2%,90.4%)显著高于眼肌型MG(34.2%,χ2=10.856,P=0.001;57.9%,χ2=12.956,P≤0.000)。甲亢组与非甲亢组MG患者titin抗体(33.3%,56.8%)与AChR抗体阳性率(55.6%,79%)差异性均无统计学意义(χ2=1.797,P=0.19;χ2=2.491,P=0.063)。结论 MG患者病情越重,titin抗体与AChR抗体阳性率越高。Titin抗体及AChR抗体能作为诊断MG的指标,联合检测能提高MG诊断的灵敏。然而MG患者血清titin抗体与AChR抗体并无一致性关系。     

Autoantibodies in thymoma-associated myasthenia gravis and their clinical significance

Myasthenia gravis (MG) is characterized by the development of antibodies that act against the acetylcholine receptor (AChR) present at the postsynaptic site of neuromuscular junctions. Some MG patients have antibodies that bind in a cross-striational pattern to skeletal and heart muscle tissue sections (striational antibodies). These antibodies react with the epitopes on the muscle protein titin, ryanodine receptor (RyR), and voltage-gated K channel α subunit, Kv1.4. Since these 3 molecules are expressed in the thymoma tissue of MG patients, striational antibodies are frequently detected in thymoma-associated MG. More severe MG symptoms in thymoma-associated MG may be due to the presence of striational autoantibodies. The anti-titin antibody, usually detected by enzyme-linked immunosorbent assay (ELISA), is found in 20-40% of all MG patients, and is more common in late-onset MG patients. The anti-RyR antibody, detected by Western blotting or ELISA, is found in 13-38% of all MG patients, and is known to inhibit Ca2+ release from sarcoplasmic reticulum and excitation-contraction coupling of the muscle. The anti-Kv1.4 antibody, detected by the immunoprecipitation assay with 35S-labeled extract from rhabdomyosarcoma cells, is found in 12-15% of all MG patients. Autoimmune myocarditis may develop in MG patients who have the anti-Kv1.4 antibody. In addition, the anti-Kv1.4 antibody is a useful marker to check the response to calcineurin inhibitors. In summary, the detection of striational antibodies provides more specific clinical information in MG patients.     

重症肌无力患者血清连接素抗体的检测及其临床意义

目的 探讨连接素（ｔｉｔｉｎ或ｃｏｎｎｅｃｔｉｎ）抗体９＝（ｔｉｔｉｎａｂ）与重症肌无力（ＭＧ）的关系。方法 应用基因工程合成重组重症肌无力胸腺瘤特异性３００００抗原（ＭＧＴ－３０蛋白）,并采用酶联免疫吸附法（ＥＬＩＳＡ）检测１４１例不同胸腺病理类型的ＭＧ患者（ＭＧ组）、２６５名健康对照者（ＮＣ组）和３６例非ＭＧ其他疾病患者（ＮＭＧ组）血清中ｔｉｔｉｎａｂ水平,同时检测ＭＧ患者血清中乙酰胆碱受体抗体（ＡＣｈＲａｂ）、突触前膜受体抗体（ＰｒｓｍＲａｂ）水平。结果 ＭＧ组血清中ｔｉｔｉｎａｂ水平明显高于ＮＣ组和ＮＭＧ组（均Ｐ〈０．０１）;阳性率以ＭＧ伴胸腺瘤（ＭＧＴ）组最高（８３．７％）,ＭＧ伴胸腺萎缩（ＭＧＡ）组其次（４３．２％０,而ＭＧ伴胸腺增生（ＭＧＨ）组及ＭＧ胸腺正常（ＭＧＮ）组患者血清中ｔｉｔｉｎａｂ均为     

Antivirus antibodies in myasthenia gravis

Serum antibodies to influenza A, measles, rubella, cytomegalovirus, varicella zoster, herpes simplex type 1, and mumps have been assayed in 104 patients with myasthenia gravis, grouped according to clinical features plus thymus pathology, and compared with matched controls. No significant differences in incidence or antibody titer were detected. In 37 patients with recent onset of symptoms, the incidence of antibody to coxsackieviruses B1-B6 was less than in controls. Juvenile-onset cases also demonstrated antibody to Epstein-Barr virus at the expected frequency. These results weaken the case for any of these common viruses, or the response to them, contributing to the pathogenesis of myasthenia gravis.     

Serum levels of pyridostigmine in myasthenia gravis: methods and clinical significance

Correlation studies on patients with myasthenia gravis are reported in which clinical assessment of fatigue and neurophysiological findings are compared to blood levels of pyridostigmine. Measurements using a high-pressure liquid chromatography method (HPLC), give reproducible results. The levels of pyridostigmine in the serum or plasma of healthy controls and of patients show no essential differences. Components of coffee, tea, chocolate and cigarettes can markedly disturb the chromatography by adding additional peaks, so that interpretation becomes difficult or impossible. Blood levels can be measured approximately one hour after oral intake of 60 mg pyridostigmine. Concentrations rise for two to four hours and then decline exponentially. The half-life of pyridostigmine was between 156 and 210 minutes. Despite identical oral dosages, the concentration differed intraindividually and interindividually among patients. While the blood level does not reach its maximum value for 1-1 1/2 to 3 hours, the maximum clinical and neurophysiological effect of pyridostigmine appears 30-60 minutes after ingestion. Variable distribution of cholinesterase inhibitors over the different compartments (blood, synaptic region) is assumed to cause this temporal lag. If the total amount of pyridostigmine is divided into 4-5 doses, the concentration profiles over the course of a day are relatively stable. There is no significant correlation between the variations in blood level throughout one day, and changes in myasthenic symptomatology. Effects of pyridostigmine can be measured at levels as low as 5 ng/ml; at levels above 40 ng/ml further improvement can be detected only rarely. Blood levels were lower if corticosteroids were administered simultaneously; azathioprine had no influence on blood levels. Blood levels assays allow better differentiation of cholinergic and myasthenic crises and the identification of disturbed absorption and interactions with other medications.     

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.     

Acetylcholine receptor antibodies in myasthenia gravis

A multivariate statistical analysis of levels of serum acetylcholine receptor antibody (AChR Ab) obtained from 197 patients with various clinical forms of myasthenia gravis (MG) was performed. Elevated AChR Ab levels are specific for MG, but normal AChR Ab levels do not rule out MG. Patients in remission or with purely ocular MG had the lowest incidence of elevation of serum AChR Ab levels, while patients with generalized, severe MG, particularly in the presence of thymoma, tended to have the greatest antibody elevations. Corticosteroids depressed AChR Ab levels, but thymectomy did not exert a consistent effect on antibody levels within a 24- to 30-month postoperative period. The relatively low 55% positivity of antibody elevations in all 197 patients probably reflects the use of heterologous (rat) AChR.     

Seronegative generalised myasthenia gravis: clinical features,antibodies, and their targets

Myasthenia gravis (MG) is a well-recognised disorder of neuromuscular transmission that can be diagnosed by the presence of antibodies to the acetylcholine receptor (AChR). However, some patients (about 15%) with generalised MG do not have detectable AChR antibodies. There is some evidence, however, that this "seronegative" MG is an antibody-mediated disorder. Plasma from patients with the disorder seems to contain various distinct humoral factors: IgG antibodies that reversibly inhibit AChR function; a non-IgG (possibly IgM) factor that indirectly inhibits AChR function; and an IgG antibody against the muscle-specific kinase (MuSK). The presence of antibodies against MuSK appears to define a subgroup of patients with seronegative MG who have predominantly localised, in many cases bulbar, muscle weaknesses (face, tongue, pharynx, etc) and reduced response to conventional immunosuppressive treatments. Moreover, muscle wasting may be present, which prevents complete response to these therapies.     

重症肌无力患者细胞免疫水平的检测及临床意义

目的 :探讨周围血中 T细胞亚群、NK细胞、细胞膜白细胞介素 - 2受体、可溶性白细胞介素 - 2受体的阳性细胞与 MG发病及临床疗效的关系。方法 :1.应用流式细胞仪检测外周围血 m IL- 2 R(CD2 5)阳性细胞、NK(CD5 6 )和T细胞亚群 (CD3 、CD4、CD8)的相对计数。 2 .用富氏双抗体夹心 EL ISA方法检测血清 s IL- 2 R。结果 :1.MG患者血清s IL- 2 R水平明显高于健康对照组 ,激素治疗后较治疗前明显下降 ;2 .NK和 CD4阳性细胞在治疗前均明显高于正常 ,治疗后明显下降 ;3.CD3 阳性细胞在激素治疗前后无明显改变 ;4.m IL- 2 R(CD2 5)阳性细胞数无明显改变。结论 :1.血清中的 s IL- 2 R,NK细胞的测定可对该病进行动态观察 ;2 .CD4增高 ,CD8下降提示免疫功能紊乱 ;3.m IL- 2 R阳性细胞百分率不能直接反映 MG的免疫功能紊乱。     

Anti-presynaptic membrane receptor antibodies in myasthenia gravis

Myasthenia gravis (MG) is considered as an autoimmune disease of neuromuscular junction resulting from antibodies directed to acetylcholine receptors (AChR). We describe the use of beta-bungarotoxin (beta-BuTx) and alpha-bungarotoxin (alpha-BuTx) to capture their corresponding proteins from preparation of crude human muscle receptor. beta-BuTx binds to presynaptic membrane receptor (PsmR) of the whole receptor fraction, while alpha-BuTx binds to AchR. The captured proteins were used as antigen in ELISA to detect antibodies to PsmR and to AchR in sera from 82 Chinese patients with MG and in controls. In MG, antibodies to PsmR only were detected in 13%, to AchR only in 11% and both to PsmR and AchR in 54%. Only 3 of 50 patients with other neurological diseases and none of 50 healthy subjects had these antibodies. Specificity tests for antibodies showed that the detection systems which we used are specific and confident. No correlation was found between antibody levels and clinical status. The significance of the PsmR antibodies in the pathogenesis of MG is unknown. We suggest that myasthenia gravis is not only due to damage of the postsynaptic membrane, but of presynaptic structures as well.     

重症肌无力病人乙酰胆碱受体抗体的测定及临床意义

用ＥＬＩＳＡ（固相酶联免疫吸附）法测定１７２例ＭＧ病人血清乙酰胆碱受体抗体（ＡｃｈＲａｂ），结果显著高于健康献血员组和非ＭＧ病人组。不同性别、病程及临床类型与ＡｃｈＲａｂ无相关性，但４１～５０岁组的显著高于其他年龄组。６７例类固醇激素治疗组、２２例大剂量两种球蛋白治疗组、１２例胸腺切除术组及３例ＭＧ危象病人２４次血浆交换疗法（ＰＥ）组，治疗后伴随肌无力症状的好转，ＡｃｈＲａｂ均显著低于治疗前。结果表明：ＡｃｈＲａｂ测定为ＭＧ诊断提供了可靠的实验依据，为类固醇激素、大剂量丙种球蛋白、胸腺切除术和ＰＥ等治疗ＭＧ提供理论依据和疗效评定的实验指标，进一步证实了ＭＧ免疫学发病机理。     

Antimuscle and antiacetylcholine receptor antibodies in myasthenia gravis

The sera of 134 patients were examined for antimuscle antibodies by immunofluorescence (IF). These derived from 77 myasthenics, 30 myasthenics with thymoma, 6 patients with thymoma and no clinical evidence of myasthenia, and 21 patients with other autoimmune or neuromuscular diseases. Three separate patterns of antimuscle antibodies could be identified in the myasthenic sera by examination of the relaxed glycerinated myofibrils by both IF and phase-contrast optics: A-band (9 with thymoma, 1 without), I-band (11 with thymoma, 17 without), and a mixed A plus I pattern (5 with thymoma, 3 without). Seventy-seven myasthenic serum samples (24 with thymoma, 53 without) were available for evaluation of antibodies to acetylcholine receptor (anti-AChR) by radioimmunoassay. Ninety-one percent reacted with crude human receptor extract and 80% with receptor extracted from denervated rat muscle. There was no correlation between the titers of anti-AChR and the presence or staining patterns of antimuscle antibodies, but patients without anti-AChR did not have antimuscle antibodies. Myasthenics with thymoma had the highest prevalence of anti-AChR (23/24) and of antimuscle antibodies (25/30), and 15 of the 20 positives stained A-bands alone or with I-band, as compared to 4 of 21 positive reactions in those without tumor. Immunoabsorption, which removed or significantly reduced anti-AChR, did not alter antimuscle reactivity. The discrepancies between anti-AChR levels and the presence and types of antimuscle antibodies suggest that these are independent autoantibodies. Current theories of immunopathogenesis implicate altered thymic antigens or a major breakdown in immune regulation, either of which could explain their production.     

Anti-MuSK antibodies: correlation with myasthenia gravis severity

The authors measured anti-muscle-specific tyrosine kinase (anti-MuSK) antibodies (Abs) in 83 serum samples from 40 patients and evaluated their correlation with myasthenia gravis severity and treatment response. Ab concentrations were often reduced by immunosuppression but not after thymectomy. Both in individual cases and in the whole population, a correlation between Ab levels and disease severity was found.     

The role of antibodies in myasthenia gravis

Myasthenia gravis is an autoimmune disease associated with antibodies directed to the postsynaptic acetylcholine receptor. These antibodies reduce the number of receptors. Autoantibodies against AChR and other muscle antigens can be used for the diagnosis of myasthenia gravis and related disorders. The origin and the role of these antibodies in the disease are discussed. Experimental autoimmune myasthenia gravis, an experimental model closely mimicking the disease, has provided answers to many questions about the role of antibodies, complement macrophages and AChR anchor proteins. Genetically modified anti-AChR antibodies may also be used in the future to treat myasthenia.     

Humoral immunity in myasthenia gravis: Biochemical characterization of acquired antireceptor antibodies and clinical correlations

The titer and characteristics of antiacetylcholine receptor antibody (A ChR-Ab) were investigated in 184 patients with myasthenia gravis. Mean A ChR-Ab titers of each clinical grade increased with the severity of the disease. A ChR-Ab was always of an IgG class. IgM (5 of 92) and IgA (2 of 48) class AChR-Ab were detected, but only concurrently with IgG and in low concentrations. IgG subclass 3 was not prominent. In 3 patients with A ChR-Ab titers in the normal range, blockade of bungarotoxin binding to receptor could still be demonstrated. A ChR-Ab from 6 patients was heterogeneous in affinity for receptor, reactivity with receptor from human ocular and gastrocnemius muscle, and blockade of toxin binding. A ChR-Ab was oligoclonal in 4 of 6 patients, as shown by concurrent production of A ChR-Ab IgG of both κ and λ types. Amniotic fluid and fetal cord serum did not interfere with antibody-receptor interaction. Variation in the pattern of weakness among patients was a function of both the heterogeneity of A ChR antibodies and the antigenic uniqueness of receptor complexes from different human muscles.