ADRB1 and familial dilated cardiomyopathy: Moreover, in order to analyze whether the reduction of IFN-γ production caused by the β1-AA-negative IgG preparation of DCM patients might have an effect of anti-β1-AR-ECI-antibodies, we added peptide corresponding to the sequence of the 1st extracellular loop of the receptor (β1-AR-ECI) as a negative control.