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Selected IgG rapidly induces Lambert–Eaton myasthenic syndrome in mice: Complement independence and EMG abnormalities
Author(s) -
Lambert Edward H.,
Len Vanda A.
Publication year - 1988
Publication title -
muscle and nerve
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.025
H-Index - 145
eISSN - 1097-4598
pISSN - 0148-639X
DOI - 10.1002/mus.880111105
Subject(s) - stimulation , lambert eaton myasthenic syndrome , stimulus (psychology) , depolarization , myasthenia gravis , motor nerve , medicine , acetylcholine , endocrinology , chemistry , anatomy , psychology , psychotherapist
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 Ca 2+ 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.