Acetylcholine receptor from human muscle is used as antigen in this radio receptor assay. The receptors are labelled with 125I-alpha-bungarotoxin. This snake venom binds the receptors most specifically and almost irreversible. Autoantibodies present in the patient´s serum attach to the labelled receptors. The resulting immune complexes are precipitated with anti-human IgG. The amount of radioactivity of the sediment is directly proportional to the concentration of acetylcholine receptor autoantibodies of the sample.
