Autoimmune myasthenia gravis (MG) is characterized by T cell and antibody responses to muscle nicotinic acetylcholine receptor (AChR). It is well known that MG as other autoimmune diseases is more prevalent in women than men and estrogen administration enhances experimental autoimmune MG (EAMG) severity. To determine whether estrogen influences EAMG pathogenesis through estrogen receptor alpha (ER alpha) activation, ER alpha knockout (KO) and wild-type (WT) C57BL/6 mice were immunized with AChR. ER alpha KO mice were equally susceptible to EAMG as WT mice and exhibited comparable antibody and immunopathological responses to AChR, suggesting a lack of involvement of ERa in EAMG pathogenesis. (C) 2011 Elsevier B.V. All rights reserved.