[Autoantibodies against the beta 1-adrenergic receptor in myocarditis and dilated cardiomyopathy: localization of two epitopes].

Sera of patients with myocarditis and dilated cardiomyopathy contain stimulatory autoantibodies directed specifically against the beta 1-adrenergic receptor. The binding of the antibodies could be localized to either the first or the second extracellular loop of the beta 1-adrenoceptor. In 73% of the cases investigated the antibodies recognized the second extracellular loop. The agonistic effects of the antibodies were abolished by beta-adrenergic antagonists. Furthermore, the antagonists were able to remove the antibodies from their binding sites.