AGTR1 and autoimmune disease: Several functional immunoglobulin G (IgG) autoantibodies targeting GPCRs are associated with autoimmune diseases, including anti-adrenergic receptors (α1AR, α2AR, β1AR, and β2AR), anti-muscarinic acetylcholine receptors (M1R–M5R), anti-endothelin receptor type A (ETAR), and anti-type 1 angiotensin II receptor (AT1R) [16].