Expression of MHC class I and II antigens and the Il-2 receptor in rejection, myocarditis and dilated cardiomyopathy.

In myocarditis and dilated cardiomyopathy a secondary immunopathogenesis is likely, since alterations to the humoral and cellular immune system have been repeatedly demonstrated. In rejection after heart transplantation activation of the immune system has been clearly seen. This may be comparable to myocarditis and thus could be a model for inflammatory heart disease. This study was set up to investigate whether an increased expression of antigens of the major histocompatibility complex and of the Il2 receptor in endomyocardial biopsies of patients after cardiac transplantation, myocarditis and dilated cardiomyopathy takes place. Cryostat sections were investigated immunohistologically by the immunoperoxidase test. There was an expression of class II antigens (HLA-DR, HLA-DP, HLA-DQ) in acute rejection and in myocarditis and in some patients with dilated cardiomyopathy on endothelial cells, interstitial cells but not on the myocytes. The results for class I (HLA-A, B, C) are similar, but in addition an expression on myocytes was observed in myocarditis and rejection. A second immunopathogenesis is most likely in some patients with dilated cardiomyopathy. The expression of the Il2 receptor on interstitial cells as a specific marker of cell activation was only seen in acute rejection and in some cases of myocarditis.