A myasthenia gravis plasma immunoglobulin reduces miniature endplate potentials at human endplates in vitro

Muscle Nerve. 1990 May;13(5):407-13. doi: 10.1002/mus.880130507.


A particular myasthenia gravis (MG) plasma Ig has previously been shown to block a single alpha-bungarotoxin (alpha-BuTx) binding site on embryonic rat muscle acetylcholine receptor (AChR). We have investigated its effect on embryonic/denervated and adult human AChR both in extracts and in situ. Plasma Ig blocked 125I-alpha-BuTx binding by greater than 85% to the AChR extracted from denervated muscle, but only by 55% to AChR extracted from normal human muscle. Incubation of intact human muscle fibers with the plasma Ig reduced 125I-alpha-BuTx binding to the endplate AChRs by 63%, and substantially decreased the amplitude of miniature endplate potentials. We conclude that anti-alpha-BuTx site antibodies, when present, can be important in the pathophysiology of the disease.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Biopsy
  • Bungarotoxins / adverse effects
  • Bungarotoxins / antagonists & inhibitors
  • Bungarotoxins / immunology
  • Evoked Potentials / drug effects*
  • Evoked Potentials / physiology
  • Humans
  • Immunoglobulins / pharmacology*
  • Immunoglobulins / physiology
  • In Vitro Techniques
  • Motor Endplate / drug effects*
  • Motor Endplate / immunology
  • Motor Endplate / physiology
  • Muscles / pathology
  • Myasthenia Gravis / blood
  • Myasthenia Gravis / etiology
  • Myasthenia Gravis / immunology*
  • Neuromuscular Junction / drug effects*
  • Receptors, Cholinergic / drug effects
  • Receptors, Cholinergic / immunology


  • Bungarotoxins
  • Immunoglobulins
  • Receptors, Cholinergic