A new model of experimental auto-immune myasthenia gravis

Origin and significance of acetylcholine and choline in plasma and serum from normal and paretic cows

Before the onset of bovine paresis a stage of hyperactivity and hypersensitivity was observed in clinical as well as in immunologically provoked cases. By gas chromatographic analysis of choline (Ch) in plasma and serum from four immunologically provoked cows this stage was verified to be an initial immuno-cholinergic hyperactivation. In the first hour after antigen challenge with 0.5 mg nematode AChE there was a very sharp rise in Ch mainly from agonist-stimulated and phospholipase mediated phosphatidylcholine (PC) breakdown. A secondary massive influx of Ca into cells was mirrored in a 1 mmol/l depression of serum-Ca values during the first hours. The hyperagonism mediated Ca-translocation brought water into cells, resulting in reduced plasma volume. The generally supposed mechanism of secondary, Ca-mediated cell damage and cell death was initiated and sometimes resulted in "Downers" with persisting paralysis. All acetylcholine (ACh)-stimulated parts from CNS to the periphery are irregularly involved explaining the very varied clinical appearance of bovine paresis, and the influence on for instance the autonomous nerve system, adrenals and pancreas. In the experimental group, ACh in plasma showed a sharp fall within the first hour, while there were fairly constant values of serum-ACh in the first four hours, possibly indicating some antibody protection. When paresis was established between 15-28 hours after challenge the general anergetic state was characterised by low ACh-levels. Also in a larger field group ACh-levels were significantly depressed in paretic compared to healthy cows. The unexpected finding in this group was considerably higher levels of ACh and especially Ch in serum compared to plasma. The origin of ACh and Ch had to be blood cells. Preliminary gas chromatographic analysis has confirmed ACh-synthesis by leucocytes and an integrated immuno-cholinergic system of great importance can be anticipated. The general feature of bovine paresis is updated by immune-etiological, pathophysiological, blood chemical, clinical-experimental and nomenclature considerations. The exact mechanism of pathogenesis is not revealed in this investigation, though many circumstances favour an anti-Id mediated hyperagonism. Other types of investigations and above all more basic knowledge of distribution and functional character of cholinergic components on immune cells are required.

The use of auto-anti-idiotypes for the visualization of acetylcholine receptors in an invertebrate skeletal muscle

Polyclonal auto-anti-idiotypic antibodies (AAIs), detected in antisera of rabbits immunized with acetylcholine conjugate, have already been characterized. In this paper, we report on a cytochemical application of these AAIs on skeletal muscle motor endplates of an invertebrate. We have shown that there is a non-uniformly distributed reaction in the synaptic cleft. The deposits seem to be associated with the muscular plasma membrane. The specificity of the cytochemical method is discussed. On this kind of muscle, the AAIs are able to detect, at the ultrastructural level, acetylcholine binding sites which most likely are acetylcholine receptors.

Isolation of an antiidiotypic antibody with acetylcholine-receptor-like binding properties from myasthenia gravis patients

The network theory predicts that a subpopulation within the antiidiotypic (anti-Id) antibody response will be the internal image of the priming stimulus. In myasthenia gravis, a portion of the anti-acetylcholine-receptor (anti-AChR) antibody repertoire is directed against the ligand-binding site. These antibodies would be expected to elicit an "anti-idiotype" which is the internal image of the receptor-binding site and hence may also bind cholinergic ligands. We have utilized this theoretical specificity to isolate anti-Id antibodies with AChR-like ligand-binding properties from the serum of 4 myasthenia gravis patients using a choline affinity column. Affinity-purified antibodies from one patient were characterized and found to exhibit binding properties similar to the AChR for various cholinergic ligands.

Immunocytochemical localization of acetylcholine receptors in locust brain using auto-anti-idiotypic acetylcholine antibodies

Auto-anti-idiotypic antibodies have been detected in antisera of rabbits immunized with an acetylcholine (ACh) conjugate. These antibodies were found to bind to ACh receptor (ACh-R) purified from different species membranes. They competed with the ACh-R antagonist alpha-bungarotoxin and some agonists such as ACh conjugate and ACh itself. They did not recognize acetylcholinesterase. Their characterization 'in vitro' suggested their employment as an immunohistological marker for ACh-R. In the locust brain, specific immunoreactivity was found in neuropils of the protocerebrum, the optic lobes, the deutocerebrum and the tritocerebrum.

Anti-acetylcholine antibodies and the pathogenesis of myasthenia gravis

Using an ELISA system, antibodies recognizing conjugated acetylcholine (ACh) were detected in sera of patients suffering from myasthenia gravis. The mean antibody level was three times higher in sera from myasthenic than from control patients. No correlation was found between anti-ACh antibody levels and anti-ACh receptor (AChR) titer. Also, the anti-ACh antibody titers were independent of sex and age of patients. Competition experiments demonstrated that the most immunoreactive compounds were choline-glutaryl-bovine serum albumin (BSA) and choline-succinyl-BSA. Antibodies present in the sera of myasthenic patients recognized an antigenic determinant mimicking conjugated ACh. The antibody affinity and specificity were sufficiently high for the detection of ACh in locust brain.

Detection of anti-acetylcholine antibodies in myasthenic patients

Antibodies, directed against an acetylcholine (ACh) conjugate, were found in the sera of myasthenic patients by using a modified enzyme-linked immunosorbent assay method. Binding of sera from control patients to the conjugate was extremely low. From competition experiments, done with compounds close to ACh, a good antibody specificity for the ACh conjugate was demonstrated in the sera of myasthenic patients. Laboratory tests will be done to help a more precise diagnostic of the disease to be given. These results may also be of value in further understanding of the process of the disease itself.