MHC class I antigens were expressed on normally negative myocytes in 38% of myocarditis cases and 68% of heart transplant rejection cases, increasing susceptibility to cytotoxic T cells.
Observational
The de novo expression of MHC class I antigens on myocytes in myocarditis and transplant rejection suggests these cells become susceptible to cytotoxic T cell-mediated damage.
Inflammation of the heart muscle is caused either by infection (i.e. coxsackie virus) resulting in myocarditis or by rejection following heart transplantation. These processes induce activation of the immune system. We examined endomyocardial biopsies from patients with myocarditis, perimyocarditis and rejection following heart transplantation and compared these to biopsies from patients with coronary artery disease. The biopsies were examined immunohistologically with specific monoclonal antibodies against class I and class II molecules of the major histocompatibility complex (MHC). MHC class I antigens on the normally negative myocytes were evident in myocarditis (38%) and in rejection after heart transplantation (68%). In the interstitium there was an increase of both MHC class I and class II antigens. MHC class II antigens, however, were never seen on myocytes. MHC class I antigens are required for the action of CD 8 positive cytotoxic T cells. Therefore myocytes which express MHC class I antigens are susceptible to cytotoxic effects of the immune system. MHC class II antigens are essential to T helper cells. By cytokine release, activated T helper cells play a central role in the initiation, regulation and mediation of an immune response in myocarditis and rejection following heart transplantation.
Hengstenberg et al. (1993) conducted an observational in Inflammatory heart disease and rejection following heart transplantation. Immunohistological examination for MHC class I and II antigens vs. Patients with coronary artery disease was evaluated on Expression of MHC class I and class II antigens on myocytes and interstitium. MHC class I antigens were expressed on normally negative myocytes in 38% of myocarditis cases and 68% of heart transplant rejection cases, increasing susceptibility to cytotoxic T cells.