ADRB2 and postural orthostatic tachycardia syndrome: Autoantibodies against muscarinic receptors M1 to M3 have been found in over 87% of patients with POTS.14 Other autoantibodies found in patients with POTS target cardiac lipid raft-associated proteins, adrenergic G-protein coupled receptors, alpha-1-adrenergic receptors, and beta-1- and beta-2-adrenergic receptors.14