Monoclonal antibodies against the main immunogenic region of the acetylcholine receptor. Mapping on the intact molecule.

About two-thirds of the antibodies to the nicotinic acetylcholine receptor (AChR) in myasthenic patients, and in rats immunized with intact AChR, bind to the main immunogenic region (MIR) on the alpha-subunit. We tested all available anti-MIR monoclonal antibodies (mAbs) by competition experiments for binding on the intact AChR from Torpedo electric organ and human muscle. Practically complete competition between all possible paired combinations of anti-MIR mAbs was found. As a consequence, the MIR must be a very concrete and small region. Furthermore, the location of the MIR relative to some other less immunogenic regions was also determined.