Beneficial effect on cardiac function by intravenous immunoglobulin treatment in patients with dilated cardiomyopathy is not due to neutralization of anti-receptor autoantibody

Anti-beta(1)-adrenoceptor (beta(1)AR) autoantibodies have been shown to be pathophysiologically important in idiopathic dilated cardiomyopathy (DCM). Treatment with intravenous immunoglobulin (IVIG) has shown beneficial effects in both DCM and ischemic cardiomyopathy. However, the underlying mechanism has not been clarified. In the present study, we therefore examined whether the improvement of cardiac function was due to neutralization of functional beta(1)AR autoantibodies by antiidiotypic antibodies. Autoantibodies against the beta(1)AR was analysed in sera from patients with DCM (n = 16) and coronary artery disease (CAD) (n = 21) treated with IVIG or placebo before, 6 and 12 months. Six month after treatment, DCM patients showed increase in beta(1)AR autoantibodies, mostly in IgG1 and IgG2, whereas in CAD patients mostly in IgG2. No changes in beta(1)AR autoantibodies after 12 months were detected. In summary, our results indicate that improvement of cardiac function by IVIG is not due to neutralization of beta(1)AR autoantibodies.