The present study documented an aberrant decrease in the percentage of B1 cells, especially in β1-AR autoantibody-positive patients, but a significant increase in the percentage of Tr cells in the peripheral blood of patients with idiopathic DCM, indicating that B1 cells and Tr cells may be involved in the pathogenesis of DCM. The gene discussed is ADRB1; the disease is familial dilated cardiomyopathy.