Aims: The aim of this study was to characterize the up-regulation of major histocompatibility complex antigens class I (HLA-A, B, C) and class II (HLA-DR), and intercellular adhesion molecule-1 with special emphasis on de novo induction of these molecules on cardiac myocytes in patients with suspected myocarditis.
Methods: Endomyocardial biopsy specimens were obtained from 83 consecutive patients. Specimens were subdivided into two groups according to clinical presentation of the disease: Group A, 58 patients with idiopathic congestive heart failure and Group B, 25 patients without heart failure. In group A, 15% of patients had active myocarditis, 36% had borderline and 48% no myocarditis according to Dallas criteria. In group B, myocarditis distribution was 12%, 36% and 52%, respectively. The major histocompatibility complex was considered to be positive when the immunoreactivity index was > or = 3+; intercellular adhesion molecules were considered positive when the score was > or = 2+.
Results: We observed two characteristic staining patterns of the HLA molecules on cardiac myocytes: (i) multifocal sarcolemmal staining at the sites of mononuclear inflammatory infiltration, (ii) linear sarcolemmal staining with otherwise normal endomyocardium. Positive immunoreactivity was observed in 60% of patients in group A, and in 44% of patients in group B. We found no correlation between a histopathological diagnosis of myocarditis or left ventricular systolic function and positive immunoreactivity.
Conclusion: The lack of correlation between immunohistological signs of active inflammation and clinical symptoms in patients with myocarditis may indicate independence of an immunological mechanism. The lack of correlation between immunoreactivity and histopathological diagnosis of myocarditis may suggest low sensitivity of traditional histological evaluation. In our opinion, the induction of major histocompatibility and intercellular adhesion molecules on cardiac myocytes may indicate an autoimmune inflammatory response in patients with inflammatory myocardial disease. Immunohistochemical methods may be helpful in selecting patients for immunosuppressive therapy.