AGE-RELATED SUSCEPTIBILITY TO EXPERIMENTAL AUTOIMMUNE MYASTHENIA-GRAVIS - IMMUNOLOGICAL AND ELECTROPHYSIOLOGICAL ASPECTS

Susceptibility to experimental autoimmune myasthenia gravis (EAMG) was found to decrease with aging in both Lewis and Brown Norway (BN) rats . In this study, the difference in susceptibility between young and ag ed Lewis and BN rats was used to analyze factors determining the clini cal severity of EAMG. The incidence and severity of muscular weak ness did not correlate with acetylcholine receptor (AChR) loss nor with th e ability of antibodies to interfere with AChR function. Aged rats sho wed significantly lower anti-rat AChR antibody titers than young rats and developed less severe or no clinical signs of disease. In individu al young or aged rats, however, no significant correlation was found b etween the clinical signs of disease and anti-rat AChR titer. Neuromus cular transmission was found to change with aging as measured by singl e-fiber electromyography (SFEMG). In aged BN rats, increased jitter an d blockings were found even before EAMG induction. Despite this distur bed neuromuscular transmission, these aged BN rats were clinically res istant against induction of EAMG. The results of this study indicate t hat the age-related susceptibility to EAMG is influenced by factors de termined by the immune attack as well as mechanisms at the level of th e neuromuscular junction. (C) 1997 John Wiley & Sons, Inc.