Immune complexes and classical complement pathway play vital roles in experimental autoimmune myasthenia gravis (EAMG). To analyze the role of immune complex receptors in EAMG, Fc gamma RIII knockout (KO) mice were immunized with AChR and were found out to be resistant to EAMG induction. This was associated with reduced neuromuscular junction deposits, lymph node cell (LNC) IL-6 production and serum complement levels. EAMG resistance of anti-Clq Ab-administered mice was also associated with reduced LNC IL-6 production and neuromuscular junction deposits, indicating Clq involvement in EAMG resistance. The data provide the first direct genetic evidence for Fc gamma receptor involvement in EAMG pathogenesis. (c) 2006 Elsevier B.V. All rights reserved.