Experimental autoimmune myasthenia gravis (EAMG) is an animal model for human myasthenia gravis (MG). Autoantibody-induced functional loss of nicotinic acetylcholine receptor (AChR) at the postsynaptic membrane is an important pathogenic feature of both MG and EAMG. To evaluate the extent at which the humoral immune response against AChR operates in the pathogenesis of EAMG, we immunized B cell knockout (mMT) and wild-type C57BL/6 mice with AChR and complete Freund’s adjuvant. The ability of AChR-primed lymph node cells to proliferate and secrete IFN-g in response to AChR and its dominant peptide a146-162 were intact in mMT mice as in wild-type mice. Similar amounts of mRNA for IFN-g, IL-4 and IL-10 in AChR-reactive lymph node cells were detected in mMT and wild-type mice. However, mMT mice had no detectable anti-AChR antibodies and remained completely free from clinical EAMG. We conclude that B cells are critically required for the genesis of clinical EAMG, but not for AChR-specific T cell priming.