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At least 541 records · Page 30Linked to original sources
PubMed2000

Treatment of passively transferred experimental autoimmune myasthenia gravis using papain.

Antibody-mediated acetylcholine receptor (AChR) loss at the neuromuscular junction, the main cause of the symptoms of myasthenia gravis, is induced by bivalent or multivalent antibodies. Passive transfer of experimental autoimmune myasthenia gravis (EAMG) can be induced very efficiently in rats by administration of intact MoAbs directed against the main immunogenic region (MIR) of the AChR, but not by their monovalent Fab fragments. We tested whether papain, which has been used therapeutically in autoimmune and other diseases, is capable of preventing EAMG by in vivo cleavage of the circulating anti-AChR antibodies into Fab fragments. EAMG was induced in 4-week-old female Lewis rats by i.p. injection of anti-MIR mAb35. A total of 0.75 mg of papain was given as one or three injections 3-7 h after MoAb injection. The mAb35 + papain-treated animals developed mild weakness during the first 30 h and subsequently recovered, while all animals that received only mAb35 developed severe myasthenic symptoms and died within 24-30 h. Animals treated only with papain showed no apparent side effects for up to 2 months. Serum anti-AChR levels in mAb35 + papain-treated rats decreased within a few hours, whereas in non-papain-treated rats they remained high for at least 30 h. Muscle AChR in mAb35 + papain-treated animals was partially protected from antibody-mediated degradation. These results show that treatment of rats with papain can prevent passively transferred EAMG without any apparent harm to the animals, and suggest a potential therapeutic use for proteolytic enzymes in myasthenia gravis.

Animals↗
PubMed1998

Influence of calcium antagonist drugs in myasthenia gravis in the elderly.

A number of drugs have been reported to cause neuromuscular blockade and/or to increase weakness in myasthenia gravis. We report on two patients, treated with felodipine and nifedipine for arterial hypertension, who presented with an exacerbation of their myasthenia gravis and a myasthenic syndrome or exacerbation of myasthenia gravis, respectively. The mechanism of action of calcium antagonist drugs at the neuromuscular junction is not yet well established, but it could be located at both presynaptic and postsynaptic levels.

Aged↗
PubMed2002

Video-assisted thoracoscopic thymectomy for myasthenia gravis.

BACKGROUND: Thymectomy is an effective, but radical therapy for myasthenia. Video-assisted thoracic surgery (VATS) may allow a minimally invasive alternative to the standard sternotomy approach. AIMS: To audit prospectively the outcome of VATS thymectomy for myasthenia gravis in a unit specializing in advanced VATS techniques. METHODS: Twenty-six patients underwent VATS thymectomy between 1997 and 2001. Most underwent preoperative plasma exchange therapy. Seventeen women and nine men with a median age of 36 years (range 17-71 years) had a right-sided VATS approach to remove all anterior mediastinal fat and thymic tissue. RESULTS: There was no perioperative mortality and all procedures were concluded successfully, with one patient requiring sternotomy. Twenty-five patients were extubated in theatre and one patient required 17 h of assisted ventilation. The other significant complication was a diathermy injury to the phrenic nerve, which recovered. Median postoperative stay was 4 days (range 2-6 days), with median postoperative chest drainage for 2 days (range 1-3 days). Three patients had progression of disease postoperatively. The remainder were asymptomatic (7), improved (14) or stable (2). CONCLUSION: In a dedicated unit with neurological and intensive care support, VATS thymectomy is a safe, effective method of obtaining remission or improvement in myasthenia gravis (MG). While achieving the same surgical goal, this approach offers advantages of improved cosmesis, shorter recovery time and minimal chest wall disruption over the gold standard of sternotomy. Better patient acceptance of this minimally invasive technique may result in wider application of the benefits of thymectomy in MG.

Adolescent↗
PubMed1999

Clinical evaluation of a staphylococcal protein A immunoadsorption system in the treatment of myasthenia gravis patients.

BACKGROUND: The role of plasma exchange is well established in the management of myasthenia gravis, an autoimmune disorder characterized by muscle weakness and caused by circulating IgG antibodies with specificity against the acetylcholine receptor. Plasma antibody removal by conventional means, however, is nonselective and uses replacement fluids (chiefly, albumin solution) derived from human plasma. STUDY DESIGN AND METHODS: The Canadian Apheresis Group undertook a study at two Canadian apheresis centers to clinically evaluate a staphylococcal protein A immunoadsorption system (EXCORIM) in myasthenia gravis patients. RESULTS: The immunoadsorption system was safe and well tolerated. Ten of 12 patients had improvement in their neurologic status, as measured by a 20-point scoring system. The mean improvement in the weakness score was significant for the group (p = 0.0013). CONCLUSION: Patients with myasthenia gravis respond to treatment with plasma immunoadsorption. Further studies are required for a cost-benefit analysis.

Adult↗
PubMed2005

Juvenile limb-girdle myasthenia gravis.

Limb-girdle myasthenia is a rare disorder which includes familial and autoimmune forms. Myasthenia gravis is an uncommon disease in children and its diagnosis may be difficult. We report here five cases of autoimmune juvenile LGM starting before the age of 16 years with attention to clinical diagnostic difficulties, evolution, laboratory and instrumental data as well as response to treatment. Diagnosis of limb-girdle myasthenia requires a strong index of suspicion also in childhood. We suggest that this form be suspected in children with unclassifiable myopathy, mostly affecting deltoid muscles and lower extremities.

Adolescent↗
PubMed1998

Morbidity after transsternal thymectomy for myasthenia gravis: a changing perspective?

A detailed assessment of recent changes in morbidity and mortality after transsternal thymectomy for myasthenia gravis is pending. To this end, a retrospective analysis was carried out of morbidity and mortality rates in 125 patients subjected to transsternal thymectomy for myasthenia gravis in the periods 1976-85 (1st decade) and 1986-95 (2nd decade). Composition of patients did not change much over time, except for more concomitant preoperative disease in the second decade (p = 0.001). None the less, complication rates were not higher, nor did the pattern of complications alter. Mortality was nil in both decades. There was no difference over the decades as to length of ventilation, intensive care treatment, or overall hospitalization. Most complications did not reveal a monocausal relationship, suggesting that a combination of risk factors was implicated. Further reductions in future morbidity rates after transsternal thymectomy for myasthenia gravis seem unlikely as patient preoperative state is unlikely to improve. In the light of the deteriorating preoperative patient condition, constant postoperative morbidity rates indicate that patient care has in fact improved.

Adult↗
PubMed1999

Early and late results after thymectomy in myasthenia gravis: a retrospective study [correction of analysis].

BACKGROUND: This study aims to evaluate the early and late outcome of patients treated by surgery for myasthenia gravis and the diagnostic value of the Besinger Score, which is based on a correlation of severity of symptoms with specific antibodies to acetylcholine receptors, in the follow-up investigation after surgical therapy. METHODS: Between June 1984 and April 1992 thoracotomy was performed in 51 myasthenia gravis cases at our department. The retrospective analysis considered patients with (n = 13) or without thymoma (n = 38). The Besinger score was used to describe the severity of disease preoperatively and up to 5 years postoperatively. RESULTS: The Besinger score fell continually post surgery. Changes in relative serum concentrations of antibodies were similar to the Besinger score. Five years after thymectomy complete remission was diagnosed in 40% of the patients. The required dosage of pyridostigmine had fallen by two thirds after 5 years. Patients with follicular hyperplasia had significantly higher remission rates than those with thymoma. CONCLUSIONS: Surgery for myasthenia gravis is successful. The Besinger score well quantifies the severity of the disease.

Adolescent↗
PubMed1980

Thymectomy in the treatment of myasthenia.

Thymectomy has been performed in 69 patients, 58 females and 11 males, age range 14 to 70 years, with a maximum in females between 20 to 30 years. Twenty-seven percent of the patients were older than 40 years. Considerable improvement resulting from remission and partial remission occurred in 89% of females and in about 50% of males, the figure for thymomatous myasthenia was about 65% in the first year after thymectomy. In the following years, improvements increased partially and the number of remissions rose as well. By chance the duration of the disease was longer than 6 years in 20% of our patients and in these a benefit from thymectomy was also found. There were 7 early deaths and 4 late deaths. Thymectomy cannot be called a cure but is an essential part of the whole treatment procedure of myasthenia comprising the administration of anticholinesterase and especially immunosuppressive agents. It was found difficult to estimate the effect of any single measure in this retrospective study by the major benefit of thymectomy is seen in initiating remissions or at least considerable improvements. Indication for operation is thought to be present in progressive myasthenia, acute or chronic, and thymoma, provided that the patient has reached an optimal condition preoperatively by adequate anticholinesterase adjustment, neurophysiological control and immunosuppressive treatment. Thymectomy is not an emergency operation and should be carefully planned. Since relapses after thymectomy are not rare, a careful neurological long-term follow-up appears obligatory.

Adolescent↗
PubMed1983

[Immunogenetics of myasthenia gravis. Significance of HLA-, complement and Cm gene systems for clinical and immunologic parameters].

In 82 non-related patients with myasthenia gravis the following immunogenetic marker systems were investigated: HLA-A, -B, -C, -DR antigens, complement polymorphisms for Bf, C3 and C4 as well as immunoglobulin allotypes G1m, G3m and Km. In 78 patients the level of circulating acetylcholin receptor autoantibody was measured. The HLA antigens showed no significant differences in frequency when compared with healthy controls. This was also true for the HLA-bound Bf and C4 polymorphism, the non-HLA-bound C3 polymorphism and the immunoglobulin allotypes. A significant (P less than 0.005) increase in heterozygote frequency of 39.7% in the Gm allotype combination G1m (1), (17); (3) when compared with an expected frequency as calculated from the gene frequency of 19.8% was found. HLA-B8 and/or HLA-DR3 positive myasthenia gravis patients showed a significantly (P less than 0.025 and less than 0.005) earlier average onset of the disease whereas in HLA-DR2 positive patients the average onset was later (P less than 0.05). The same HLA antigens correlated with quantitative differences in the acetylcholine receptor autoantibodies: HLA-B8 and/or -DR3 positive patients had on average higher antibody levels than HLA-B8 or -DR3-negative patients. The difference for HLA-DR3 was statistically significant (P less than 0.05). On the other hand patients with HLA-DR2 antigens had significantly lower antibody levels (P less than 0.025). Increased mean antibody levels were also seen in G1m(1), (17) allotype (P less than 0.005) and G3m(21) (P less than 0.05). As the HLA antigens and Gm allotype genes are situated on different chromosomes (C6 and C14) two distinct gene regions are identified in myasthenia gravis. These are associated with quantitative differences in acetylcholine receptor antibody titres.

Autoantibodies↗
PubMed1981

[Myasthenia syndrome during chloroquine treatment (author's transl)].

Myasthenic reaction with partial neuromuscular block in the electromyogram and increased antibodies against acetylcholine-receptor protein developed during chloroquine administration over two months in a 52-year-old man known for eight years ot have rheumatoid arthritis. When the drug was discontinued and pyridostigmine administration begun, myasthenia improved within six weeks and had completely disappeared after three months. During the same period abnormal neuromuscular transmission regressed. Also, the significantly increased antibodies against acetylcholine-receptor protein became normal. It remains undecided whether this was a drug-induced myasthenia gravis or only a latent myasthenia manifested by the drug.

Arthritis, Rheumatoid↗
PubMed1976

Detection of anti-acetylcholine receptor factors in serum and thymus from patients with myasthenia gravis.

Since the blood and thymus of patients with myasthenia gravis may contain inhibitors of neuromuscular transmission that affect acetylcholine receptors of striated muscle, we used denervated rat muscle to test for inhibitors in 43 serums and 18 thymus glands from such patients. Seven per cent of serums inhibited the binding of 125l alpha-bungarotoxin to triton-solubilized receptors; 65 per cent interfered with binding of toxin-labeled receptors to concanavalin-A coupled to Sepharose gel, and 85 per cent formed IgG-receptor complexes detectable by immunoprecipitation. Serum inhibitory activity varied widely among patients with similar clinical manifestations and was not correlated with duration of myasthenia gravis or thymectomy. Among thymus extracts, 44 per cent were inhibitory in the concanavalin-A binding assay, whereas 72 per cent contained anti-receptor IgG. Thus, serums from patients with myasthenia gravis contain more than one anti-receptor factor.

Acetylcholine↗
PubMed1977

Myasthenia gravis. Study of humoral immune mechanisms by passive transfer to mice.

To study the role of humoral factors in the pathogenesis of myasthenia gravis, we employed passive transfer of human serum fractions to mice. Immunoglobulins from 16 patients with myasthenia gravis were injected into mice daily for one to 14 days. Typical myasthenic features of reduction in amplitude of miniature end-plate potentials (mean change more than 50 per cent, P less than 0.005) or reduction in acetylcholine receptors at neuromuscular junctions (mean change more than 50 per cent, P less than 0.005) (or both) were produced by immunoglobulin from 15 of the 16 patients. Some mice showed weakness or decremental responses to repetitive nerve stimulation as well. The active fraction was identified as IgG by three different purification methods. Its effect was enhanced by the third component (C3) of the complement system, but the fifth component (C5) had no effect. These data suggest that the pathogenesis of myasthenia gravis often involves and antibody-mediated autoimmune attack on the acetylcholine receptors of the neuromuscular junction.

Acetylcholine↗
PubMed1979

Identification of two serum components regulating the expression of T-lymphocyte function in childhood myasthenia gravis.

We studied serums and cells from nine children with myasthenia gravis to determine whether there were alterations in the distribution or function of different T-lymphocyte subpopulations. The low numbers of E-rosette-forming T lymphocytes and their failure to respond to antigen by producing normal suppressor T cells were correlated with the presence of an IgG antibody directed toward the theophylline-sensitive T-cell subset; this activity could be blocked by d-tubocurarine. Incubation of normal T lymphocytes with serum from patients rendered the cells "myasthenia-like" when assayed for E-rosettes and for antigen-induced suppressor-cell function. A second, non-IgG factor found in patients' serums had activity like that of thymic hormone and induced T-cell maturation in normal bone marrow. This factor was not inhibited by d-tubocurarine; its activity was strongest in the two patients most severely affected, and it disappeared after thymectomy in both these patients. We conclude that in childhood myasthenia gravis there may be two independent serum factors; one an IgG antibody directed at a subset of T lymphocytes, blocked by d-tubocurarine and apparently unaffected by thymectomy, and the other a thymus factor that induces T-lymphocyte maturation.

Antigens↗
PubMed1990

Steroids induce acetylcholine receptors on cultured human muscle: implications for myasthenia gravis.

Antibodies to the acetylcholine receptor (AChR), which are diagnostic of the human autoimmune disease myasthenia gravis, block AChR function and increase the rate of AChR degradation leading to impaired neuromuscular transmission. Steroids are frequently used to alleviate symptoms of muscle fatigue and weakness in patients with myasthenia gravis because of their well-documented immunosuppressive effects. We show here that the steroid dexamethasone significantly increases total surface AChRs on cultured human muscle exposed to myasthenia gravis sera. Our results suggest that the clinical improvement observed in myasthenic patients treated with steroids is due not only to an effect on the immune system but also to a direct effect on muscle. We propose that the identification and development of pharmacologic agents that augment receptors and other proteins that are reduced by human genetic or autoimmune disease will have broad therapeutic applications.

Autoantibodies↗
PubMed1996

Peptide analogs to pathogenic epitopes of the human acetylcholine receptor alpha subunit as potential modulators of myasthenia gravis.

Myasthenia gravis is an autoimmune disease in which T cells specific to epitopes of the autoantigen, the human acetylcholine receptor, play a role. We identified two peptides, p195-212 and p259-271, from the alpha subunit of the receptor, which bound to major histocompatibility complex (MHC) class II molecules on antigen-presenting cells (APCs) from peripheral blood lymphocytes of myasthenia gravis patients and stimulated lymphocytes of >80% of the patients. We have prepared analogs of these myasthenogenic peptides and tested their ability to bind to MHC class II determinants and to interfere specifically with T-cell stimulation. We first determined relative binding efficiency of the myasthenogenic peptides and their analogs to APCs of patients. We found that single substituted analogs of p195-212 (Ala-207) and p259-271 (Lys-262) could bind to human MHC molecules on APCs as efficiently as the original peptides. Moreover, dual analogs containing the two single substituted analogs in one stretch (either sequentially, Ala-207/Lys-262, or reciprocally, Lys-262/Ala-207) could also bind to APCs of patients, including those that failed to bind one of the single substituted analogs. The single substituted analogs significantly inhibited T-cell stimulation induced by their respective myasthenogenic peptides in >95% of the patients. The dual analogs were capable of inhibiting stimulation induced by either of the peptides: They inhibited the response to p195-212 and p259-271 in >95% and >90% of the patients, respectively. Thus, the dual analogs are good candidates for inhibition of T-cell responses of myasthenia gravis patients and might have therapeutic potential.

Adult↗
PubMed2026

Genetic evidence supports the prioritization of CD40 among prespecified immune-related candidate drug targets in myasthenia gravis.

AIM: To prioritize prespecified immune-related candidate drug targets in myasthenia gravis for further validation based on integrated genetic evidence. METHODS: We integrated drug-target Mendelian randomization (MR) using cis-expression quantitative trait loci (cis-eQTLs), protein-level MR of plasma CD40 abundance using plasma protein quantitative trait loci (pQTLs), and colocalization analyses to evaluate genetically proxied associations with overall MG, early-onset myasthenia gravis (EOMG), and late-onset myasthenia gravis (LOMG). RESULTS: In this study, CD40 showed the most consistent genetic evidence among the six prespecified targets. Effect estimates are reported as odds ratios (ORs) with 95% confidence intervals (CIs). Higher CD40 expression proxied by cis-eQTLs was associated with increased risk of overall MG (OR = 1.14, 95% CI: 1.05-1.24, Bonferroni-adjusted p = 0.022) and EOMG (OR = 1.32, 95% CI: 1.12-1.56, Bonferroni-adjusted p = 0.015). Genetically predicted higher plasma CD40 protein abundance was associated with increased overall MG risk (OR = 1.31, 95% CI: 1.08-1.57, Bonferroni-adjusted p = 0.010), whereas the protein-level MR result for EOMG was directionally consistent but not statistically significant. Colocalization analysis provided suggestive but not definitive evidence of colocalization between CD40 expression and EOMG risk. FCGRT, IL2RA, and SYK showed additional exploratory MR signals requiring further validation. CONCLUSION: CD40 showed the most consistent genetic support among the prespecified targets, supporting its prioritization for functional validation and further therapeutic investigation in MG.

CD40↗
PubMed2005

Increased expression of rapsyn in muscles prevents acetylcholine receptor loss in experimental autoimmune myasthenia gravis.

Myasthenia gravis is usually caused by autoantibodies to the acetylcholine receptor (AChR). The AChR is clustered and anchored in the postsynaptic membrane of the neuromuscular junction (NMJ) by a cytoplasmic protein called rapsyn. We previously showed that resistance to experimental autoimmune myasthenia gravis (EAMG) in aged rats correlates with increased rapsyn concentration at the NMJ. It is possible, therefore, that endogenous rapsyn expression may be an important determinant of AChR loss and neuromuscular transmission failure in the human disease, and that upregulation of rapsyn expression could be used therapeutically. To examine first a potential therapeutic application of rapsyn upregulation, we induced acute EAMG in young rats by passive transfer of AChR antibody, mAb 35, and used in vivo electroporation to over-express rapsyn unilaterally in one tibialis anterior. We looked at the compound muscle action potentials (CMAPs) in the tibialis anterior, at rapsyn and AChR expression by quantitative radioimmunoassay and immunofluorescence, and at the morphology of the NMJs, comparing the electroporated and untreated muscles, as well as the control and EAMG rats. In control rats, transfected muscle fibres had extrasynaptic rapsyn aggregates, as well as slightly increased rapsyn and AChR concentrations at the NMJ. In EAMG rats, despite deposits of the membrane attack complex, the rapsyn-overexpressing muscles showed no decrement in the CMAPs, no loss of AChR, and the majority had normal postsynaptic folds, whereas endplates of untreated muscles showed typical AChR loss and morphological damage. These data suggest not only that increasing rapsyn expression could be a potential treatment for selected muscles of myasthenia gravis patients, but also lend support to the hypothesis that individual differences in innate rapsyn expression could be a factor in determining disease severity.

Action Potentials↗