Screening of serum autoantibodies to cardiac beta(1)-adrenoceptors and M-2-muscarinic acetylcholine receptors in 408 healthy subjects of varying ages

Autoantibodies to cardiac beta(1)-adrenoceptors and M-2-muscarinic receptor s have mainly been found in the sera of patients with idiopathic dilated ca rdiomyopathy (DCM). In order to elucidate the pathological significance of these autoantibodies in DCM, it is necessary to understand their characteri stic distribution in a healthy population of different genders and ages. Th e peptides corresponding to the sequences of the second extracellular loops of the human beta(1)-adrenoceptor and M-2-muscarinic receptors were theref ore used as antigens to screen the sera of 408 healthy subjects of differen t ages (ranging from 0.5 to 85 Sears). Of 408 sera, 41 (10.0%) and 46 (11.3 %) recognized the beta(1)-adrenoceptor and M-2-muscarinic receptor peptides respectively, Of the positive sera for beta(1)-adrenoceptors and M-2-musca rinic receptors, up to 63.4% and 56.5% had both anti-beta(1)-adrenoceptor a nd anti-M-2-muscarinic receptor autoantibodies respectively. The antibody t itres of the positive sera of healthy subjects were all of a low level, wit h a geometric mean titre of 1:42 +/- 1.9 for anti-beta(1)-adrenoceptor anti bodies and 1:51 +/- 1.7 for anti-M-2-muscarinic receptor antibodies. The fr equency of occurrence of autoantibodies to both receptors in the sera of he althy subjects increased significantly with age. In conclusion, the autoantibodies to beta(1)-adrenoceptors and M-2-muscarin ic receptors in the sera of healthy subjects are characterized by a low fre quency of occurrence and low titre, with the frequency of occurrence increa sing with age.