Function of circulating antibody to acetylcholine receptor in myasthenia gravis: investigation by plasma exchange.

Plasma exchange has been used to investigate the function fo anti-acetylcholine receptor (anti-AChR) antibody in seven patients with acquired myasthenia gravis (MG) who had elevated antibody titers and in one patient with congenital MG who had normal titers. There was an inverse association between clinical indices of muscle strength and anti-AChR titers, with a minimum time lag of 2 days for the clinical response. The inverse association of the clinical state with anti-AChR antibody titers was closer than that with total immunoglobulin G or other immunoglobulins, and is consistent with the view that the anti-AChR antibody is the principal factor interfering with neuromuscular transmission in acquired MG.