Monoclonal antibodies used to probe acetylcholine receptor structure: localization of the main immunogenic region and detection of similarities between subunits.

Abstract

Seventeen cell lines producing monoclonal antibodies against Torpedo californica (torpedo) acetylcholine receptor (AcChoR) and its subunits were established. By using these antibodies as probes, the following were identified: a similar antigenic determinant on .alpha. and .beta. torpedo subunits, a similar antigenic determinant on .gamma. and .delta. subunits, antigenic determinants unique for .alpha. or .beta. torpedo AcChoR subunits, a small region on the .alpha. subunit that dominates the immunogenicity of native torpedo AcChoR in rats (a monoclonal antibody directed at this region could bind to rat AcChoR in vivo and cause passive experimental autoimmune myasthenia gravis), and antigenic determinants on torpedo subunits recognized in AcChoR from other species. The unexpected similarities between .alpha. and .beta. and between .gamma. and .delta. subunits raise the possibility that the complex 4 subunit structure of AcChoR was derived from a simpler precursor and suggests that these antigenic similarities might reflect some structural and functional homologies.