Screening of Serum Autoantibodies to Cardiac β₁-adrenoceptors and M₂-muscarinic Acetylcholine Receptors in 408 Healthy Subjects of Varying Ages

Abstract

Autoantibodies to cardiac β₁-adrenoceptors and M₂-muscarinic receptors have mainly been found in the sera of patients with idiopathic dilated cardiomyopathy (DCM). In order to elucidate the pathological significance of these autoantibodies in DCM, it is necessary to understand their characteristic distribution in a healthy population of different genders and ages. The peptides corresponding to the sequences of the second extracellular loops of the human β₁-adrenoceptor and M₂-muscarinic receptors were therefore used as antigens to screen the sera of 408 healthy subjects of different ages (ranging from 0.5 to 85 years). Of 408 sera, 41 (10.0%) and 46 (11.3%) recognized the β₁-adrenoceptor and M₂-muscarinic receptor peptides respectively. Of the positive sera for β₁-adrenoceptors and M₂-muscarinic receptors, up to 63.4% and 56.5% had both anti-β₁-adrenoceptor and anti-M₂-muscarinic receptor autoantibodies respectively. The antibody titres of the positive sera of healthy subjects were all of a low level, with a geometric mean titre of 1:42 ± 1.9 for anti-β₁-adrenoceptor antibodies and 1:51 ± 1.7 for anti-M₂-muscarinic receptor antibodies. The frequency of occurrence of autoantibodies to both receptors in the sera of healthy subjects increased significantly with age.

In conclusion, the autoantibodies to β₁-adrenoceptors and M₂-muscarinic receptors in the sera of healthy subjects are characterized by a low frequency of occurrence and low titre, with the frequency of occurrence increasing with age.

Key Words:

• Autoantibody
• β₁-adrenoceptor
• M₂-muscarinic receptor
• Healthy population