The beta 1-adrenoceptor as antigen: functional aspects.

The sera of patients with myocarditis and idiopathic dilated cardiomyopathy contain agonistic autoantibodies that bind to the beta 1-adrenoceptor. These antibodies recognize epitopes on either the first or second extracellular loop of this receptor and exert in cultured neonatal rat heart myocytes a positive chronotropic effect. This effect is eliminated by beta 1-adrenoceptor blockade as well as by peptides corresponding to the first or second extracellular loop of the human beta 1-adrenoceptor. The antibodies realize their effects mainly via the beta-adrenoceptor-adenylate cyclase-protein kinase A cascade.