NPPB and familial dilated cardiomyopathy: Although the mechanism by which a decrease in B1 cell numbers aggravates DCM is unclear, this pilot study reveals that decreased in the percentage of B1 cells are closely related to the decrease in the LVEF, the increase NT-proBNP levels and the increase in β1-AR autoantibody levels, indicating that decreased B1 cell numbers will exacerbate the deterioration of cardiac function and the progression of heart failure in patients with DCM.