Abstract
Of 7 rat monoclonal antibodies directed against nicotinic acetylcholine receptor, the 3 whose binding was blocked by .alpha.-bungarotoxin produced acute paralysis in chicken hatchlings, whereas the 4 others had no effect. In the effected animals, weakness and decremental EMG responses appeared within 1 h after i.v. injection and both abnormalities improved after anticholinesterase administration. No histologic changes were seen in the muscle of injected animals. Antibodies binding in relationship to the cholinergic binding site, and presumably producing pharmacologic blockade of acetylcholine receptor, may play an important role in the pathogenesis of the defective neuromuscular transmission in myasthenia gravis.