A myasthenia gravis plasma immunoglobulin reduces miniature endplate potentials at human endplates in vitro.
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.
Burges
J
J
Department of Pharmacology, Royal Free Hospital School of Medicine, London, UK.
Wray
D W
DW
Pizzighella
S
S
Hall
Z
Z
Vincent
A
A
D001706:Biopsy; D002038:Bungarotoxins / Q000009:adverse effects / Q000037:antagonists & inhibitors / Q000276:immunology; D005071:Evoked Potentials / Q000187:drug effects* / Q000502:physiology; D006801:Humans; D007136:Immunoglobulins / Q000494:pharmacology* / Q000502:physiology; D066298:In Vitro Techniques; D009045:Motor Endplate / Q000187:drug effects* / Q000276:immunology / Q000502:physiology; D009132:Muscles / Q000473:pathology; D009157:Myasthenia Gravis / Q000097:blood / Q000209:etiology / Q000276:immunology*; D009469:Neuromuscular Junction / Q000187:drug effects*; D011950:Receptors, Cholinergic / Q000187:drug effects / Q000276:immunology
D002038:Bungarotoxins; D007136:Immunoglobulins; D011950:Receptors, Cholinergic