Abstract
The diagnosis of acquired myasthenia gravis (MG) in apparently seronegative individuals is aided by finding immunoglobulin complexed to acetylcholine receptors (AChR) and a reduction in the number of binding sites for a-bungarotoxin (α-BTx) in nerve-muscle biopsies. In this study, we found that anti-AChR antibodies in extracellular fluidscan complex with cytoplasmic epitopes of AChR in the process of muscle extraction. When normal muscle was briefly exposed to antibodies (0.3 nmol/1) in the initial step of tissuehomogenization (before detergent extraction) membranous AChR became complexed with IgG. This was so even with a nonmyasthenogenic monoclonal antibody specific for the α-subunit's presumptive cytoplasmic segment 366–389. We also found that antibodies reactive with AChR's α-BTx binding region can significantly lower apparent yields of α-BTx binding sites extracted from muscle. Thus, the finding of IgG complexed to AChR extracted from biopsied muscle does not necessarily reflect in vivo binding but, nevertheless, is a sensitive indicator of AChR seropositivity in patients suspected to have MG.
Original language | English (US) |
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Pages (from-to) | 218-222 |
Number of pages | 5 |
Journal | Neurology |
Volume | 42 |
Issue number | 1 |
DOIs | |
State | Published - Jan 1992 |
ASJC Scopus subject areas
- Clinical Neurology