DILATED CARDIOMYOPATHY DEFINES SERUM AUTOANTIBODIES AGAINST G-PROTEIN-COUPLED CARDIOVASCULAR RECEPTORS

In order further to identify the prevalence of anti-receptor autoantib odies in the sera of patients with dilated cardiomyopathy (DCM), we at tempted to detect autoantibodies against a series of G-protein-coupled cardiovascular receptors in a well-defined population of DCM patients from Japan. Peptides corresponding to the sequences of the second ext racellular loops of the human beta(1) and beta(2) adrenoceptors, alpha (1) adrenoceptors, M2 muscarinic acetylcholine receptors and angiotens in II-1 (AT1) receptors were used as antigens in an enzyme immunoassay to screen the sera from patients with DCM (n = 28). Nine sera from pa tients with DCM (37%,) and 2 sera from healthy subjects (9%) recognize d the beta(1) adrenoceptor peptide. Ten sera from patients (36%) and 3 sera from healthy subjects(13%) recognized the M2 receptor peptide. T hirty-six per cent of the patients with autoantibody against the beta( 1) adrenoceptor had autoantibody against the M2 receptor. However, no significantly high frequencies of autoantibodies against the beta(2) a drenoceptor, alpha(1) adrenoceptor and AT1 receptor were found in DCM patients, Our results demonstrate that a subgroup of patients with DCM have a specific spectrum of autoantibodies which are specifically dir ected against the second extracellular loops of the beta(1) adrenocept ors and M2 muscarinic receptors rather than other cardiovascular recep tors.