Circulating cardiac autoantibodies in dilated cardiomyopathy and myocarditis: pathogenetic and clinical significance.
Dilated cardiomyopathy (DCM) is a relevant cause of heart failure and a common indication for heart transplantation. It may be idiopathic, familial/genetic, viral, autoimmune or immune-mediated associated with a viral infection. Myocarditis is an inflammatory disease of the myocardium; it may be idiopathic, infectious or autoimmune and may heal or lead to DCM. Thus, in a patient subset, myocarditis and DCM are thought to represent the acute and chronic stages of an organ-specific autoimmune disease of the myocardium. In keeping with this hypothesis, autoimmune features in patients with myocarditis/DCM include: familial aggregation; a weak association with HLA-DR4; abnormal expression of HLA class II on cardiac endothelium on endomyocardial biopsy; and detection of organ- and disease-specific cardiac autoantibodies of the IgG class in the sera of affected patients and symptom-free relatives. The cardiac autoantibodies detected by immunofluorescence are directed against multiple antigens. Two of these, first identified using immunoblotting and confirmed by ELISA, are the atrial-specific alpha- and the ventricular and skeletal muscle beta-heavy chain isoform. The alpha-myosin isoform fulfils the expected criteria for organ-specific autoimmunity, in that immunization with cardiac, but not skeletal myosin reproduces, in susceptible mouse strains, the human disease phenotype of myocarditis/DCM; in addition, alpha-myosin is entirely cardiac-specific. Additional antigenic targets of heart-reactive autoantibodies include unknown sarcolemmal proteins, mitochondrial enzymes, beta-adrenergic and muscarinic receptors. For some of these antibodies, there is in vitro evidence for a functional role. The organ-specific cardiac autoantibodies detected by immunofluorescence in symptom-free relatives were associated with echocardiographic features suggestive of early disease. Mid-term follow-up suggests that these antibodies are predictive markers of progression to DCM among symptom-free relatives with or without abnormal echocardiographic findings.
Caforio
Alida L P
AL
Division of Cardiology, Department of Clinical and Experimental Medicine, University of Padua, Policlinico Universitario, Centro 'V. Gallucci', via N. Giustiniani, 2, Italy. alida.caforio@unipd.it
Mahon
Niall J
NJ
Tona
Francesco
F
McKenna
William J
WJ
D000918:Antibody Specificity / Q000276:immunology; D001323:Autoantibodies / Q000097:blood*; D002311:Cardiomyopathy, Dilated / Q000235:genetics / Q000276:immunology*; D000939:Epitopes / Q000276:immunology; D006333:Heart Failure / Q000235:genetics / Q000276:immunology; D006801:Humans; D009205:Myocarditis / Q000235:genetics / Q000276:immunology*; D009206:Myocardium / Q000276:immunology*; D024723:Ventricular Myosins / Q000276:immunology
D001323:Autoantibodies; D000939:Epitopes; D024723:Ventricular Myosins