Assessment of immune modulation of beta-adrenergic pathways in human dilated cardiomyopathy: influence of...

Sera from patients with dilated cardiomyopathy contain autoantibodies modifying cardiac beta-adrenergic pathways. The influence of the methodology used to determine the prevalence of these antibodies was examined by comparing in 51 patients with idiopathic dilated cardiomyopathy the results of three assays: (1) isoproterenol-sensitive adenylate cyclase; (2) ligand binding inhibition; (3) enzyme-linked immunoassay (ELISA) of beta-receptor peptides. In 20% of the patients, all three tests gave positive results, while the concordance of the adenylate cyclase assay with either of the other two tests was 65%. ELISA was positive for a beta 1-receptor peptide corresponding to the second extracellular loop, but negative for a beta 2-receptor peptide. The results suggest that autoantibodies in dilated cardiomyopathy sera interact with several components of the beta-receptor-adenylate cyclase, and therefore a combination of methodologic approaches is needed to evaluate the prevalence and consequences of beta-receptor autoimmunity.