β-银环蛇毒素结合蛋白抗体和乙酰胆碱受体抗体亲和性及其在重症肌无力致病中的意义

为了研究β-银环蛇毒素(β-BuTx )结合蛋白在重症肌无力(MG)致病中的作用和意义。我们用牛膈肌乙酰胆碱受体(AChR)和β-BuTx结合蛋白分别免疫Lewis鼠。结果显示AChR免疫鼠能诱导典型的实验性重症肌无力(EAMG)临床症状和血清中高效价的抗AChR抗体。β-BuTx结合蛋白免疫鼠组血清中虽然也能检测到较高效价的β-BuTx结合蛋白抗体,但未观察到明确的EAMG症状。分析和比较了两组免疫鼠血清抗体的亲和指数后发现,β-BuTx结合蛋白抗体亲和指数明显低于AChR抗体亲和指数。我们认为:β-BuTx结合蛋白在实验动物中具有抗原性,但它的抗体亲和性远较AChR为低,这可能是β-BuTx结合蛋白缺乏致Lewis鼠肌无力的重要因素之一。     

乙酰胆碱受体α亚基125-147肽段制作实验性重症肌无力动物模型的研究

目的研究用乙酰胆碱受体α亚基125-147(Tα125-147)肽段制作实验性重症肌无力(EAMG)的动物模型。方法给实验组Lewis鼠(12只)皮下注射人工合成电鳗乙酰胆碱受体Tα125-147肽段,观察接种后鼠的肌力变化,应用低频重复电刺激检测电衰减反应及酶联免疫法检测血清乙酰胆碱受体抗体(AChR-Ab)滴度;并与对照组鼠(8只)比较。结果在第2次接种后1周实验组6只鼠逐渐出现肌无力症状,11只鼠低频重复电刺激电衰减反应( )及血清AChR-Ab( );对照组鼠均无肌无力症状,低频重复电刺激电衰减反应(-),血清AChR-Ab7只鼠(-),1只(±),两组比较差异有显著性(均P<0.01)。结论用人工合成乙酰胆碱受体Tα125-147肽段免疫Lewis鼠可以成功制作EAMG动物模型。     

实验性重症肌无力大鼠模型的研究

目的从丁(氏)双鳍电鳐的电器官分离乙酰胆碱受体(AChR)免疫大鼠,建立实验性自身免疫性重症肌无力(EAMG)动物模型.方法参照徐浩鹏等方法从丁(氏)双鳍电鳐的电器官提取AChR蛋白,并采用Folin-酚试剂法及酶联免疫吸附法(ELISA)检测提取蛋白的含量及活性;以提取的蛋白主动免疫Lewis大鼠,每天观察其临床表现,并于免疫后7周进行低频重复电刺激、单纤维肌电图及血清中乙酰胆碱受体抗体(AchRAb)水平检测.结果提取蛋白的含量为35.4 mg/mL,AChR提取物可与阳性血清中的AChRAb发生结合反应.免疫后1周左右,实验组有3只大鼠出现轻度肌无力症状,持续2～5 d自行缓解;免疫后5周左右实验组8只大鼠均表现出不同程度肌无力症状.实验组大鼠低频重复电刺激阳性率达75%,其衰减率明显高于对照组.实验组大鼠单肌纤维动作电位平均连续差(MCD)值与正常对照组比较明显延长(P＜0.01),而福(氏)完全佐剂(CFA)对照组与正常对照组间MCD值差异无显著性.实验组大鼠AChRAb水平明显高于CFA对照组(P＜0.01);实验组7只大鼠AChRAb的P/N值≥2.1,而CFA对昭组P/N值均＜1.4.结论从丁(氏)双鳍电鳐电器官提取的AChR蛋白成功地诱导成EAMG动物模型,可为进一步研究重症肌无力创造一定条件.     

抗乙酰胆碱受体单克隆抗体A7诱导实验性自身免疫性重症肌无力作用

目的探讨抗乙酰胆碱受体单克隆抗体A7(抗AChRmAbA7)对实验性自身免疫性重症肌无力(EAMG)的作用。方法经Lewis大鼠腹腔注射5mL20倍浓缩的含抗AChRmAbA7培养上清液,建立EAMG被动转输模型。对照组经腹腔注射同体积的PBS。每8h监测体重和临床症状评分。48h后处死实验动物。采用放射免疫法检测AChR,并计算出AChR损失率。结果抗AChRmAbA7诱导的EAMG模型AChR损失率高达243%~452%,而且AChR损失率与临床症状评分相关(r=074,P<001)。抗AChRmAbA7攻击位点在终板的AChR上。结论抗AChRmAbA7可用于诱导EAMG模型及有关研究。     

NKT细胞活化对实验性自身免疫性重症肌无力的影响

目的选取NKT细胞刺激物α-GalCer,经不同时间点腹腔注射小鼠,使其激活NKT细胞,观察对实验性自身免疫性重症肌无力(EAMG)临床表现及其相关免疫指标的影响,从而为治疗EAMG提供新的途径。方法建立C57BL/6小鼠EAMG的动物模型,选取刺激物α-GalCer腹腔注射,通过CD1d递呈引起Vα14+NKT细胞的激活,观察小鼠体重、临床表现及相关免疫指标的变化,探讨不同时间点NKT细胞激活对EAMG产生的效应。结果在C57BL/6小鼠,Vehicle组EAMG的发生率为90%,平均发病天数37±6;α-GalCer预防组疾病的发生率为30%,平均发病天数为51±9。结论a-GalCer提前免疫能激活NKT保护C57BL/6小鼠发生EAMG,该结果为EAMG和其他自身免疫病的防治提供了依据。     

白细胞介素-12对实验性自身免疫性重症肌无力耐受的影响

目的探讨白细胞介素(IL)-12对未成熟树突状细胞(iDC)诱导实验性自身免疫性重症肌无力(EAMG)耐受的影响。方法采用乙酰胆碱受体(AChR)负载的iDC接种Lewis大鼠,IL-12组大鼠在接种DC的同时和次日分别给予重组大鼠白细胞介素-12(rrIL-12)腹腔注射,200 ng/次。3周后以AChR和完全福氏佐剂(CFA)进行免疫,观察免疫7周后大鼠重症肌无力(MG)相关指标的改变。结果接种AChR负载的iDC的大鼠和健康大鼠经AChR和CFA免疫后MG相关指标无明显改变;而经IL-12干预的大鼠和EAMG对照组大鼠均产生明显的MG症状,重复电刺激出现明显衰减,血清AChR抗体滴度明显增高,神经肌肉接头呈现典型的MG样改变。结论 IL-12可阻止AChR负载的iDC诱导EAMG耐受,提示DC功能异常和IL-12可能在MG异常免疫反应的启动机制中具有重要作用。     

实验性自身免疫性重症肌无力模型大鼠腓肠肌低密度脂蛋白受体相关蛋白4表达的特点

目的探讨实验性自身免疫性重症肌无力(EAMG)模型大鼠腓肠肌低密度脂蛋白受体相关蛋白4(LRP4)表达的特点。方法将30只大鼠随机分为EAMG组、对照组和空白组。以小鼠乙酰胆碱受体(AChR)基因为模板合成AChR抗原,以Lewis大鼠为免疫动物。EAMG组采取主动免疫法将AChR抗原与弗氏佐剂混合制成乳剂,注射入大鼠背部皮下。对照组在相同部位注射等量的弗氏佐剂。空白组在相同部位注射等量的生理盐水。8周后使用低频重复电刺激(RNS)检测肌电RNS衰减率。采用蛋白免疫印迹法检测腓肠肌LRP4含量。结果 EAMG组所有大鼠在8周后出现肌无力症状,对照组、空白组大鼠无肌无力症状。EAMG组大鼠RNS衰减率明显高于对照组和空白组(均P0.05)。EAMG组大鼠腓肠肌LRP4蛋白的相对含量明显低于对照组和空白组(均P0.05)。结论 EAMG大鼠中,当AChR被自身抗体破坏时,可能导致包含LRP4在内的整条信号通路受损,进而使LRP4含量减少。LRP4是神经肌肉接头信号通路完整的重要分子。     

鼠源乙酰胆碱受体α亚基97-116肽段免疫Lewis鼠诱导实验性重症肌无力模型

重症肌无力(MG)是一种主要累及神经肌肉接头突触后膜乙酰胆碱受体,由乙酰胆碱受体抗体(AchR-Ab)介导的自身免疫性疾病[1]。实验性重症肌无力(EAMG)在临床表现及免疫发病机制上类似人类MG,因此被用于MG发病机制及防治方法的基础研究。经典的EAMG模型是由电鳗电器管中提取的AchR免疫易感鼠诱导而成,但获得足够量纯化的AchR较为困难,国内尤是如此。近几十年来研究者们一直尝试用人工合成的肽段作为免疫原诱导EAMG,但效果均不理想。本实验尝试用鼠源乙酰胆碱受体α亚基97-116肽段(R97-116)复制EAMG模型,希望为国内MG的基础研究提供…     

用AChR单克隆抗体建立大鼠重症肌无力被动转移模型的研究

目的利用乙酰胆碱受体(AChR)单克隆抗体建立重症肌无力(MG)被动转移模型。方法将AChR单克隆抗体mAb35注入3种品系大鼠腹腔，观察其临床症状并行药理学和电生理学及超微结构鉴定。结果被动转移mAb35后3种大鼠均可出现肌无力症状。其临床症状、药理学特点、电生理特点和超微结构变化均与MG患者相似。结论利用AChR单克隆抗体可在此3种品系大鼠成功建立获得性自身免疫性MG模型。     

实验性自身免疫性重症肌无力大鼠CD28/CTLA-4:B7表达水平的研究

目的探讨实验性自身免疫性重症肌无力(EAMG)大鼠外周血单个核细胞(PBMC)CD28/CTLA4B7的表达水平。方法健康、雌性Lewis大鼠24只,随机分为正常组、EAMG组、完全福(氏)佐剂(CFA)对照组。EAMG组大鼠分别于足垫、腹部及背部皮下多点注射丁(氏)双鳍电鳐电器官乙酰胆碱受体蛋白乳剂1mL,第4周再次注射上述乳剂免疫大鼠。CFA对照组只接受等量的CFA皮下注射。初次免疫后7周分离PBMC,应用RTPCR和流式细胞术分析方法,分别进行CD28、CTLA4mRNA及B71、B72蛋白表达水平检测。结果(1)正常组大鼠PBMCCD28、CTLA4mRNA表达水平较低,尤其CTLA4mRNA仅有极少量表达;前二者在EAMG组大鼠表达水平均明显增加(P<0001),而正常组和CFA对照组之间表达水平差异无显著性(P>005)。(2)正常大鼠B71、B72在PBMC上仅少量表达而EAMG组表达明显增加(P<0001),正常组与CFA对照组比较差异均无显著性(P>005)。结论EAMG大鼠存在PBMCCD28/CTLA4B7协同刺激分子的表达异常,CD28/CTLA4B7共刺激通路可能参与了机体异常免疫反应的诱导与维持,在重症肌无力(MG)的发生过程中发挥重要作用。     

Clinical correlation of anti-receptor antibody titer, sensitivity to curare and electromyographic changes in experimental autoimmune myasthenia gravis

Experimental autoimmune myasthenia gravis (EAMG) was studied in 39 rabbits which were repeatedly immunized with purified membrane-bound Torpedo (Nacine timilei) acetylcholine receptor (N-AchR). These rabbits invariably formed anti-AChR antibodies and some of them developed muscular weakness or flaccid paralysis. Pharmacological, physiological and ultrastructural studies showed that the pathological features of EAMG in rabbits closely resembled those of human myasthenia gravis. Antibody titer to AChR of the rabbit sera was determined with ELISA. In some of the rabbits, a rise in antibody Level occurred without appearance of weakness, while it is still likely that AChR antibody could be necessary for the induction of neuromuscular blockage. The sensitivity to curare was found to correlates closely with the severity of the disease. Typical electromyographic changes were found only in some of the EAMG rabbits with these studies. It was considered that anti-AChR concentration would not be the single pathological factor in EAMG.     

The relationship between anti-acetylcholine receptor antibody levels and neuromuscular function in chronically myasthenic rats

Rats immunized with acetylcholine receptor protein (AChR) purified from Torpedo electric organ develop defects of neuromuscular function closely mimicking those of myasthenia gravis. These rats are easily fatigued, have reduced neuromuscular transmission, and high titers of anti-AChR antibody. Contrary to previous findings however, the present study finds a very good correlation between the development of the anti-rat AChR antibody levels and subsequent decreases in neuromuscular function in experimentally myasthenic animals. This result supports the hypothesis that anti-AChR antibody levels play a central role in development of experimental myasthenia. The relevance of these findings to the pathology of myasthenia gravis is considered.     

Analysis of contractile properties of muscles from rats immunized with purified acetylcholine receptor

Experimental autoimmune myasthenia gravis (EAMG) was induced in rats by injection of purified acetylcholine receptor (AChR). In addition to detecting elevated serum titers of anti-AChR antibodies, we observed decreased twitch-tension at submaximal stimulation voltages and increased curare sensitivity by muscles obtained from immunized rats when compared to muscles obtained from nonimmune control rats. Furthermore, antibody-induced neuromuscular impairment was expressed to differing extents dependent on whether the diaphragm, soleus, or extensor digitorum longus muscle was examined. Thus, we conclude that potential antibody perturbation of AChR function will depend not only on the nature of the antibody, but also on the complex structure-function relationships that exist in individual muscles. This may partially explain the variable impairment of different muscle groups in patients with myasthenia.     

Protective potential of experimental autoimmune myasthenia gravis in Lewis rats by IL-10-modified dendritic cells

Dendritic cells (DC) are usually regarded as antigen-presenting cells (APC) involved in T cell activation, but DC also directly or indirectly affect B cell function, antibody synthesis and isotype switch. In this study, we explore potential of DC-based immunotherapy in ongoing experimental autoimmune myasthenia gravis (EAMG) in Lewis rats, which is mediated by anti-acetylcholine receptor (AChR) antibodies. Spleen DC were isolated from onset of Lewis rat EAMG on day 39 post immunization (p.i.), exposed in vitro to IL-10 and then injected intraperitoneally into ongoing EAMG Lewis rats at dose of 1 x 10(6) cells/rat on day 5 p.i. with AChR + complete Freund's adjuvant. IL-10-modified DC resulted in lower clinical scores, less body weight loss, lower numbers of anti-AChR IgG antibody-secreting cells and lower affinity of anti-AChR antibodies in rats receiving IL-10-modified DC, accompanied with lower expression of CD80 and CD86 and lower lymphocyte proliferation among lymph node mononuclear cells compared with control EAMG rats. Lower levels of IL-10 and IFN-gamma were also found in the supernatants of AChR-stimulated lymph node MNC culture in rats receiving IL-10-modified DC. These results demonstrate that IL-10-modified DC induced hypo-responsiveness by down-regulating co-stimulatory molecules, and reduced production of anti-AChR antibodies possibly by inhibiting IL-10 production. Importantly, this procedure that autologous DC from EAMG were adopted to treat ongoing EAMG is more close to clinical trial in human, encouraging future evaluation in human myasthenia gravis.     

Suppression of experimental autoimmune myasthenia gravis in IL-10 gene-disrupted mice is associated with reduced B cells and serum cytotoxicity on mouse cell line expressing AChR

To analyze the role of interleukin-10 (IL-10) in experimental autoimmune myasthenia gravis (EAMG) pathogenesis, we induced clinical EAMG in C57BL/6 and IL-10 gene-knockout (KO) mice. IL-10 KO mice had a lower incidence and severity of EAMG, with less muscle acetylcholine receptor (AChR) loss. AChR-immunized IL-10 KO mice showed a significantly higher AChR-specific proliferative response, altered cytokine response, lower number of class II-positive cells and B-cells, but a greater CD5(+)CD19(+) population than C57BL/6 mice. The lower clinical incidence in IL-10 KO could be explained not by a reduction of the quantity, but by a possible difference in the pathogenicity of anti-AChR antibodies.     

α-Bungarotoxin sensitization in experimental autoimmune myasthenia gravis

A mouse model of MG, termed experimental autoimmune myasthenia gravis (EAMG), can be obtained after immunization with Torpedo acetylcholine receptor (AChR). Although many studies have detailed the consequence of AChR antibodies binding at the neuromuscular junction and the difficulty in obtaining obvious clinical signs, less attention has been focused on the possibility of amplifying the muscular block in order to discriminate between immunized and healthy animals. In the present studies we observe that a single inoculation of α-bungarotoxin (α-bgt) can amplify the neuromuscular block revealed by repetitive nerve stimulation, and induce in EAMG mice a stable muscular weakness state lasting for at least 169 hours instead of 95 hours in normal mice. This model could provide an excellent tool for evaluating drugs active on neuromuscular transmission. © 1993 John Wiley & Soncs, Inc.     

C5a is not involved in experimental autoimmune myasthenia gravis pathogenesis

C5 deficient mice are highly resistant to experimental autoimmune myasthenia gravis (EAMG) despite intact immune response to acetylcholine receptor (AChR), validating the pivotal role played by membrane attack complex (MAC, C5b-9) in neuromuscular junction destruction. To distinguish the significance of C5a from that of C5b in EAMG pathogenesis, C5a receptor (C5aR) knockout (KO) and wild-type (WT) mice were immunized with AChR to induce pathogenic anti-AChR antibodies. In contrast with C5 deficient mice, C5aR KO mice were equally susceptible to EAMG as WT mice and exhibited comparable antibody and lymphocyte proliferation response to AChR implicating that C5a is not involved in EAMG development.     

Neonatal tolerance to an immunodominant T cell reactivity does not confer resistance to EAMG induction in Lewis rats

The overall goal of this study was to determine, during induction of experimental autoimmune myasthenia gravis (EAMG) in Lewis rats, the relative importance of acetylcholine receptor (AChR)-reactive helper T cells associated with one particular immunodominant fine specificity. Thus, experiments presented below were designed to evaluate the immunopathological role played by helper T cells with reactivity against the AChR alpha subunit region associated with amino acid residues 100–116 (i.e., α100–116); in particular, the relationship between T cell reactivity with this specificity and disease induction was assessed. In order to examine the importance of this T cell reactivity, Lewis rat neonates were made T cell tolerant to a synthetic peptide α100–116 and subsequently evaluated for anti-AChR antibody production and resulting neuromuscular dysfunction. Results indicated that although T cell reactivity against the α100–116 peptide could be effectively removed from the Lewis T cell repertoire, tolerized Lewis rats immunized with AChR could undergo an active anti-AChR antibody response that produced symptoms of EAMG. Thus, other AChR T cell reactivities appeared capable of providing adequate help to B cells leading to production of anti-AChR antibodies with pathogenic potential.     

Morphologic and immunologic studies in experimental autoimmune myasthenia gravis and myasthenia gravis.

An indirect immunoperoxidase technique was used to study by light microscopy the binding of serum from experimental autoimmune myasthenia gravis (EAMG) rabbits to junctionally and extrajunctionally located acetylcholine receptors (AChRs) in human and rat muscles. Binding was restricted to junctional AChR. Alpha bungarotoxin (a-BGT) partially blocked the binding of EAMG serum, while myasthenia gravis serum, carbamylcholine, decamethonium, and tubocurarine did not. A radioimmunoassay showed significant binding of antibodies in EAMG sera to 125l AChR. This binding was not inhibited by a-BGT, nor by carbamylcholine, decamethonium, or tubocurarine. Sera from 10 myasthenia gravis patients did not contain antibodies binding to the 125l AChR. We suggest that EAMG in rabbits induced by Torpedo AChR differs serologically from myasthenia gravis in patients, probably owing to antigenic differences between Torpedo and human AChR, and that antigenic differences also exist between junctional and extrajunctional receptors.     

Lymphotoxin-alpha deficiency completely protects C57BL/6 mice from developing clinical experimental autoimmune myasthenia gravis

A complete prevention of clinical experimental autoimmune myasthenia gravis (EAMG) was observed in lymphotoxin (LT)-alpha deficient (LT-alpha(-/-)) mice compared to LT-alpha(+/+) mice when immunized with acetylcholine receptor. However, only a partial prevention of clinical EAMG incidence was observed in LT-beta(-/-) mice compared to LT-beta(+/+) mice. LT-alpha(-/-)and LT-beta(-/-) mice had lower mean titers of total IgG, IgG(1), IgG(2a) and IgG(2b) and higher or equal mean titers of IgM anti-AChR antibodies compared to controls. Therefore, LT-alpha(-/-)and LT-beta(-/-) AChR immunized mice are capable of mounting a primary (IgM) humoral immune response to AChR, but are less capable of switching to the pathogenic anti-AChR IgG isotypes. LT could play a significant role in the pathogenesis of myasthenia gravis.