ADRB1 and autoimmune disease: The reason for this discrepancy is not fully understood; however, recent studies showed a reduction in the level of specific anti-GPCRs autoantibodies, including anti-β1AR and anti-ETAR autoantibodies, in the sera of patients with autoimmune diseases, and acute coronary syndrome, compared with healthy donors [13,42], potentially attributed to autoantibody adherence to its respective receptor and subsequently decreased serum availability [42].