Autoantibodies against M2-muscarinic acetylcholine receptors: new upstream targets in atrial fibrillation in patients with dilated cardiomyopathy.
OBJECTIVE
To characterise the clinical significance of M2-muscarinic acetylcholine receptor autoantibodies (M2-AAB) in patients with dilated cardiomyopathy (DCM).


RESULTS
Sera from 104 patients with DCM, age-matched with 104 patients with idiopathic atrial fibrillation (Af) and 104 healthy control subjects, were screened for M2-AAB by enzyme-linked immunosorbent assay (ELISA). IgG purified by Protein-A column was also used as a primary antibody in ELISA. In DCM, M2-AAB were detected in 40% of patients using whole sera and in 36% of patients using purified IgG. M2-AAB were also found in several patients with idiopathic Af (23%, 23%), and these frequencies were significantly higher than those in healthy subjects (8%, 8%). Af was more common in AAB-positive than in AAB-negative patients with DCM. Multivariable analysis confirmed that M2-AAB were independent predictors of the presence of Af in such patients. We determined electrophysiological changes by adding patient purified M2-AAB to chick embryos. Purified IgG from both Af and DCM patients exhibited negative chronotropic effects and induced supraventricular arrhythmias.


CONCLUSIONS
M2-AAB may play a role in mediating the development of Af in patients with DCM.
Baba
Akiyasu
A
Department of Medicine, Kitasato Institute Hospital, Tokyo, Japan. baba-a@kitasato.or.jp
Yoshikawa
Tsutomu
T
Fukuda
Yukiko
Y
Sugiyama
Takashi
T
Shimada
Megumi
M
Akaishi
Makoto
M
Tsuchimoto
Kanji
K
Ogawa
Satoshi
S
Fu
Michael
M
D001281:Atrial Fibrillation / Q000276:immunology*; D001323:Autoantibodies / Q000032:analysis*; D002311:Cardiomyopathy, Dilated / Q000150:complications / Q000276:immunology*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000032:analysis; D008297:Male; D008875:Middle Aged; D043585:Receptor, Muscarinic M2 / Q000276:immunology*
D001323:Autoantibodies; D007074:Immunoglobulin G; D043585:Receptor, Muscarinic M2