Selected IgG rapidly induces Lambert-Eaton myasthenic syndrome in mice: complement independence and EMG abnormalities

Muscle Nerve. 1988 Nov;11(11):1133-45. doi: 10.1002/mus.880111105.


Antibodies in individual patients with the Lambert-Eaton myasthenic syndrome (LES) differ in their reactivity with mouse motor nerve terminals. Of 26 LES patients' sera injected a single time into mice, 3 caused a highly significant reduction in stimulus-dependent quantal release (m) of acetylcholine (ACh) (to 6, 33, and 42 quanta per impulse at 1 Hz, respectively; mean for 10 control sera, 100 quanta at 1 Hz). The most potent serum (LES-A) was fully effective in mice deficient in complement component C5 and in mice depleted of complement components C3----C9 by cobra venom factor. A single i.v. injection of serum reduced m in direct proportion to log dose. Responses to K+ depolarization and increasing concentrations of Ca2+ were like those observed in human LES. With LES-A serum, or its IgG, m was reduced near maximally in 1 day and plateaued in 3-4 days. Recovery began after day 8; m was in the normal range by day 20-30. Electromyographic (EMG) abnormalities were not seen until m fell below 40 quanta per impulse at 1 Hz. Below 10 quanta, clinical signs of weakness appeared, and the EMG abnormalities were those classically associated with LES: a marked reduction of compound muscle action potential to a single nerve stimulus in rested muscle, a further decrement during stimulation at slow rates, but marked facilitation during rapid repetitive stimulation.

Publication types

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

MeSH terms

  • Acetylcholine / metabolism
  • Animals
  • Calcium / physiology
  • Complement System Proteins / immunology
  • Electromyography*
  • Female
  • Humans
  • Immunoglobulin G / administration & dosage
  • Immunoglobulin G / immunology*
  • Injections
  • Mice
  • Myasthenia Gravis / immunology*
  • Myasthenia Gravis / physiopathology
  • Neurons / immunology
  • Potassium / physiology


  • Immunoglobulin G
  • Complement System Proteins
  • Acetylcholine
  • Potassium
  • Calcium