[Study of antibodies to motor end-plate in ocular myasthenia gravis]

This study was undertaken to investigate whether serum obtained from ocular MG with undetectable antibodies contains antibodies which bind to normal motor end-plates immunohistochemically. Nineteen patients with ocular MG were studied. Anti-AChR antibodies in serum were assayed by an immunoprecipitation method using human junctional AChR as the antigen. Anti-AChR antibodies in serum which bind to the junctional AChR at the motor end-plates were detected immunohistochemically by incubating the muscle with each serum. Bound IgG was detected by peroxidase labeled protein A (P-PA). IgG deposit at the own limb muscle motor end-plates (biceps brachii) was also detected by P-PA. Anti-AChR antibodies in serum were positive in 9 out of 19 patients and IgG antibodies bound to the junctional AChR were demonstrated in 16 of 19 patients. IgG bound to own end-plates was observed in 13 of 14 patients studied. In 2 patients IgG was detected at the own end-plates, but not at the not-self end-plates. These findings indicate that detection of IgG at the limb muscle end-plates serves for the diagnosis of ocular MG with undetectable antibodies in serum and anti-AChR antibodies in some patients may react exclusively with the autologous AChR.