CELLULAR MESSENGER-RNA EXPRESSION OF INTERFERON-GAMMA (IFN-GAMMA), IL-4 AND IL-10 RELATES TO RESISTANCE TO EXPERIMENTAL AUTOIMMUNE MYASTHENIA-GRAVIS (EAMG) IN YOUNG LEWIS RATS

Age-related alterations in the immune system, including changes in lym phocyte subset composition, result in changes of cytokine patterns and might thereby influence the incidence and severity of autoimmune dise ases. To investigate the age-related resistance to EAMG, an animal mod el for human MG, young (4-week-old) and adult (8-10-week-old) female L ewis rats were immunized with Torpedo acetylcholine receptor (AChR) an d Freund's complete adjuvant (FCA). Adult Lewis rats showed severe wei ght loss and progressive muscular weakness after immunization, while y oung rats developed minor clinical signs of EAMG after a prolonged int erval post-immunization. By comparison with adult rats, the young had lower AChR-specific T and B cells responses, and less muscle AChR loss . In situ hybridization performed on mononuclear cells (MNC) from lymp h nodes revealed that young rats had lower levels of AChR-specific IFN -gamma, IL-4 and IL-10 mRNA-expressing cells compared with adult rats. Since IFN-gamma, IL-4 and IL-10 promote the development of EAMG, the low expression of these cytokines might contribute to EAMG resistance in young Lewis rats.