Alloantigen profile of graft vascular endothelial cells in rat heart allograft rejection: expression of MHC and non-MHC alloantigens

The alloantigen profile of vascular endothelial cells has been studied in a rat experimental model for MHC-mismatched and MHC-matched (non-MHC mismatched) allogeneic heart transplantation (TX). Hearts were studied for alloantibody deposition in the graft vasculature and the occurrence of vasculopathy. In addition reactivity of allosera with in vitro cultures of graft-type vascular endothelial cells was examined. Alloantibodies were seen deposited in the graft vasculature in MHC-mismatched as well as in MHC-matched TX. In MHC-matched hearts the most dominant vasculopathy consisted of early arteriosclerotic lesions. In vitro studies demonstrated that, in addition to MHC alloantigens, heart vascular endothelial cells express non-MHC alloantigens. These endothelial non-MHC alloantigens are constitutively expressed by heart endothelial cells, and expression is not influenced by cytokine stimulation. We conclude that humoral immune response against these endothelial non-MHC alloantigens may play an important role in development of graft vasculopathy and particularly of arteriosclerotic lesions.