Muscle acetylcholine receptors complexed with autologous IgG reflect seropositivity but not necessarily in vivo binding

Masato Sano, Edward H. Lambert, Daniel J. McCormick, Vanda A. Lennon

Research output: Contribution to journalArticle

12 Scopus citations

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 languageEnglish (US)
Pages (from-to)218-222
Number of pages5
JournalNeurology
Volume42
Issue number1
StatePublished - Jan 1992

ASJC Scopus subject areas

  • Clinical Neurology

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