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

Anti-β1-adrenoceptor (β1AR) 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 β1AR autoantibodies by anti-idiotypic antibodies. Autoantibodies against the β1AR 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 β1AR autoantibodies, mostly in IgG1 and IgG2, whereas in CAD patients mostly in IgG2. No changes in β1AR autoantibodies after 12 months were detected.In summary, our results indicate that improvement of cardiac function by IVIG is not due to neutralization of β1AR autoantibodies.