Autoantibodies in D-penicillamine-induced myasthenia gravis: a comparison with idiopathic myasthenia and rheumatoid arthritis.

The distribution of autoantibodies was studied in patients with rheumatoid arthritis (RA) treated by D-penicillamine and who developed myasthenia gravis (MG). The anti-human acetylcholine receptor (AChR) antibodies were specifically associated with clinical symptoms of MG without any difference in the pattern of specificities in idiopathic (id-MG) or in induced MG (DPen-MG). Conversely, anti-nuclear antibodies were elevated in DPen-MG sera compared to id-MG sera (P less than 0.001) but were also compared to patients with RA treated by D-penicillamine (or thiopronine) and who did not develop MG. Anti-denatured DNA antibodies were enhanced in sera from treated patients, whether they had presented or not a MG disease. Anti-histone antibodies were associated with RA. These observations suggest that the immunological imbalance in RA patients, can be increased by a drug treatment which may trigger the appearance of a second autoimmune disease such as MG, where anti-AChR antibodies are associated with anti-nuclear antibodies.

Myasthenic sera recognize the human acetylcholine receptor bound to thymopoietin.

The thymic hormone, thymopoietin (Tpo), from human (HTpo), bovine (BTpo) and from synthetic (sHTpo) origins bound to the acetylcholine receptor (AChR) solubilized by Triton 1.5% from human muscle. This binding was demonstrated either by inhibition of formation of radiolabeled alpha bungarotoxin (alpha Bgt)-AChR complexes measured after precipitation by ammonium sulfate or by a myasthenic serum containing a high concentration of anti-AChR antibodies, or directly by incubating the human AChR with radiolabeled sHTpo or BTpo. The 125I-labeled alpha Bgt-AChR complexes were totally inhibited by 10(-6) M sHTpo or BTpo. The complexes formed by AChR and the radiolabeled Tpo were recognized specifically by sera containing anti-AChR antibodies from myasthenic patients. The active pentapeptide derivative of Tpo, thymopentin, another thymic hormone, thymulin, as well as bovine insulin did not interfere with the specific binding of alpha Bgt to human AChR. Tpo and anti-AChR antibodies could participate together in the inhibition of neuromuscular conduction with Tpo modulating the depressive effect of the antibodies on the neuromuscular junction in myasthenia gravis.

Increased binding of anti-acetylcholine receptor antibodies to thymic antigen in patients with myasthenia gravis and other autoimmune diseases, as compared to those with myasthenia gravis alone.

We compared the binding activity against acetylcholine receptors solubilized from human muscle (AChRM) and human thymus (AChRT), of sera from patients with myasthenia gravis (MG) alone, to those of sera from patients with myasthenia gravis and associated autoimmune diseases (MG AD). The sera of the MG AD group bound relatively better to thymic antigen (86% vs. 62%). This group was found to contain a higher proportion of women over 40 years of age (more than 50% of the group). The expression of a particular AChR antigen in normal human thymus may be one of the factors involved in the pathogenesis of MG, especially when this disease is associated with other autoimmune disorders.

Expression vectors based on the Agrobacterium rhizogenes Ri plasmid transformation system.

This article describes several new expression vectors that capitalize on the ability of Agrobacterium rhizogenes to transfer DNA from its Ri plasmid to the plant nuclear genome. The intermediate vectors described include an expression cassette based on one of the three following promoters: the nopaline synthase promoter, or the cauliflower mosaic virus (CaMV) promoters responsible for transcription of either the 19S or 35S CaMV RNA. The termination and polyadenylation signals are either from the nopaline synthase gene or from CaMV. The expression micro-Ri plasmid described bears a selectable marker gene and an expression cassette cloned between the borders of the TL-region of the Ri plasmid of A. rhizogenes A4. Different strategies for using these vectors to introduce chimeric genes into plants are described, and the advantages and disadvantages of the two types of vectors are discussed.

[Myasthenia induced by D-penicillamine. Study of immuno-clinical correlations in 23 cases]. / Myasthénie induite par la D-pénicillamine. Etude des corrélations immuno-cliniques dans 23 cas.

Sera from 23 patients with D-penicillamine-induced myasthenia gravis (MG) contained antibodies directed against the human muscle acetylcholine receptor (anti-AChR) in 83% of the cases at the onset of the disease. Twenty-one were patients with rheumatoid arthritis. The anti-AChR antibody titers were comparable to those of sera from ocular MG patients and were related to the presence of clinical signs but not to their severity. The anti-AChR antibodies persisted in autonomous MG (5 cases) and disappeared in the other cases. The same phenomenon occurred for antinuclear antibodies detected in sera from 13 patients at the onset of the disease: anti-ss DNA 9/13, antinuclear 4/13 and anti-histones 7/13. The latter antibodies seem to result from, and follow the D-penicillamine treatment.

Evidence for the presence of immunoreactive acetylcholine receptors on human thymus cells.

Triton extracts from thymuses and thymomas from either normal subjects or MG patients specifically bind [125I] alpha-bungarotoxin (alpha Bgt). This binding is saturable (apparent Ks = 5.9 X 10(-9) M) and can be inhibited by cold alpha Bgt, acetylcholine or nicotinic agonists. These results demonstrate the presence on human thymus cells of acetylcholine receptor (ACh.R), 2.8% for normal human thymus in regard of ACh.R concentration in human muscle. Normal human thymic extracts were used as an antigen source in the radioimmunoassay for the detection of anti-ACh.R antibodies in positive MG patients' sera. 72% of these sera were also positive with the thymic antigen. The demonstration of ACh.R in human thymus brings further support to the hypothesis of intrathymic autosensitivity against ACh.R as a major factor in MG pathogenesis.

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.

[Assay of acetylcholine receptor antibodies in myasthenia gravis. A study of 329 sera (author's transl)]. / Le dosage des anticorps anti-récepteurs de l'acétylcholine dans la myasthénie. Etude de 329 sérums.

Antibodies directed against acetylcholine receptors were investigated in 329 sera by a radioimmunological technique using human muscle. Eighty-six per cent of patients with generalized myasthenia gave positive results. The percentage of positivity reached 90% when a receptor lipid extract was used. Fifty-six per cent of 25 sera from patients with ocular myasthenia were positive. Conversely, no antibody was detected in controls (other neurological diseases, normal subjects), except for two lupus patients. In addition to its diagnostic value, the assay of antibodies to acetylcholine receptors proved useful in the follow-up of myasthenic patients (notably neonates) treated by thymectomy, immunodepressants and plasmapheresis.

A lipid-associated acetylcholine receptor as an antigen in diagnosis of myasthenia gravis.

Antibodies to the acetylcholine receptor are detected in over 85% of myasthenic patients' sera when acetylcholine receptors extracted from human muscle are used as the antigen. As recent data have shown the importance of the lipid environment for receptor function, we have used a lipid-associated acetylcholine receptor as the antigen for antibody determination. This fraction was shown to discriminate better between normal human sera and sera from myasthenic patients with low antibody titres. Among 12 sera from myasthenic patients in which antibodies were undetectable with the delipidated receptor as the antigen, seven were positive with the lipid-associated receptor. This lipid-associated fraction could be used beneficially for research and clinical investigation.

[Determination of anti-acetylcholine receptor antibodies in myasthenia and its treatment by plasma exchange and immunosuppressants]. / Le dosage des anticorps anti-récepteurs d'acétyl-choline (R. ACh) dans la myasthénie et son traitement par échanges plasmatiques (E.P.) et immunosuppresseurs (I.S.).

Recent works have confirmed the auto immune mechanism in myasthenia gravis, that Simpson had hypothetized early as 1960. A post synaptic blockage, of which Ach-R antibodies seem to be chiefly responsible, is now accepted though the exact pathogenesis remains unknown. The immuno assay of these antibodies is still difficult; their blood level evaluates the course of the disease and the effectiveness of the treatment. The withdrawal of the antibodies by plasma exchange (P.E.) and the inhibition of their secretion by immunosuppression (I.S.) lead to remission in many cases. Principle of the immuno assay and results of P.E. and I.S. are reported in 21 cases.