Autoimmunity against the ryanodine receptor in myasthenia gravis

Some myasthenia gravis (MG) patients have antibodies against skeletal muscl e antigens in addition to the acetylcholine receptor (AChR). A major antige n for these antibodies is the Ca2+ release channel of the sarcoplasmic reti culum the ryanodine receptor (RyR). These antibodies are found mainly in MG patients with a thymoma MG and correlate with severe MG symptoms. The anti bodies recognize a region near the N-terminus on the RyR, which seems to be of importance for RyR regulation. The antibodies cause allosteric inhibiti on of RyR function in vitro, inhibiting Ca2+ release from sarcoplasmic reti culum.