[Heterogeneity of acetylcholine receptor antibodies in patients with myasthenia gravis].

Antibodies against the nicotinic acetylcholine receptor in sera of 21 myasthenia gravis patients were checked for their ability to block or split binding of alpha-bungarotoxin to the human acetylcholine receptor. Affinity-purified acetylcholine receptors from human skeletal muscle were used in parallel in the common precipitation assay and an inhibition assay. Cross-reactivity of acetylcholine receptor antibodies was analyzed with receptor preparation from different species (calf, rat, Torpedo c. and Electrophorus e.), purified identically to high specific activity. An antibody pattern was set up for each patient and related to the clinical state of the disease. alpha-Bungarotoxin-inhibiting antibodies were demonstrable in 74% of myasthenia gravis patients, alpha-bgt displacing antibodies were found in 39% of the investigated sera. Broad cross-reactivity with acetylcholine receptors from other mammalian muscle was evident (calf 75%, rat 90%) only very few sera reacted with acetylcholine receptors from electric fish (Torpedo c. 14%, Electrophorus e. 38%). Antibody concentrations determined by using xenoantigens were much lower than those obtained by human acetylcholine receptor. The lack of a clear-cut correlation between the amount of serum antibodies and the clinical state of myasthenia gravis can be explained by the established antibody-heterogeneity, shown by a constant antibody pattern characteristic for each patient. However, between this specific antibody pattern and the state of the disease no correlation could be established either.