ENDOTHELIAL-CELLS IMMUNOLOGY AND GRAFT-REJECTION

Endothelial cells play a critical role in the induction of graft rejection. Endothelial cell adhesion molecules, specialized in the interactions with leukocytes, are essential for the recruitment of recipient immunocompetent cells inside allografts. Furthermore, endothelial cells, stimulated by the cytokines secreted by recipient immune cells, might behave as antigen-presenting cells, contributing to the maintenance of the immune reaction against the graft. Endothelial cells are also targets of the graft rejection, as shown by the importance of vascular lesions in all forms of rejection, hyperacute, acute or chronic. Endothelial lesions are immunologically induced by both humoral and cellular mechanisms. Circulating anti-endothelial antibodies, most often natural, might induce, in a complement dependent fashion, endothelial cell lysis. Stimulated cytotoxic T lymphocytes and NK cells are also able to provoke endothelial alterations in grafted tissue. Immunomodulation and protection of the endothelium are therefore an important aim to achieve for the improvement of graft survival and tolerance.