Selected IgG rapidly induces Lambert–Eaton myasthenic syndrome in mice: Complement independence and EMG abnormalities

Edward H. Lambert, Vanda A. Lennon

Research output: Contribution to journalArticle

49 Scopus citations


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.

Original languageEnglish (US)
Pages (from-to)1133-1145
Number of pages13
JournalMuscle & Nerve
Issue number11
StatePublished - Nov 1988

ASJC Scopus subject areas

  • Physiology
  • Clinical Neurology
  • Cellular and Molecular Neuroscience
  • Physiology (medical)

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