Antibodies against beta 1 and beta 2 adrenergic receptors in myasthenia gravis

Patients with myasthenia gravis have antibodies and T cells that react with the beta 1- and beta 2-adrenergic receptors. These receptors, as well as o ther auto-antigens, are present on cardiomyocytes, skeletal muscle cells an d lymphocytes and are of importance for the regulation of the functions of these organs. Antibodies against the beta 1-adrenergic receptor have been i mplicated in dilated cardiomyopathies. Myasthenia gravis (MG) patients have been suggested to have a higher than normal prevalence of heart disease. W e have analysed the isotypes, subclasses, and binding sites of the beta-adr energic receptors antibodies in both MG patients and healthy individuals an d the correlation between beta-adrenergic receptors antibodies and heart di sease in MG patients. The patients have IgG antibodies that react with both beta 1- and beta 2-adrenergic receptors. The subclasses were predominantly IgG2 and IgG4. By using synthesised overlapping peptides representing the immunodominant regions an the receptors, it was shown that the antibodies b ound to partially overlapping sites on both beta 1- and beta 2-adrenergic r eceptors, but not to peptides from the acetylcholine receptor. beta-adrener gic receptor antibodies were found in 34/125 MG patients. Seven out of thes e 34 patients had symptomatic heart disease, all seven were over 70 years o f age and had arteriosclerotic heart disease. There was no difference in th e prevalence of clinical heart disease in patients with and without beta-ad renergic receptor antibodies. However, patients with heart disease had sign ificantly higher levels of antibodies than healthy individuals and other pa tients. Antibodies against beta-adrenergic receptors in patients with myast henia gravis binds to both beta 1- and beta 2-adrenergic receptors and migh t be implicated in the few patients with myasthenia gravis who have heart d isease. (C) 1998 Elsevier Science B.V. All rights reserved.