In organ transplantation, blood borne cells and macromolecules (eg, antibodies) of the host
immune system are brought into direct contact with the endothelial cell lining of graft vessels.
In this location, graft endothelial cells play several roles in allograft rejection, including the
initiation of rejection responses by presentation of alloantigen to circulating T cells; the
development of inflammation and thrombosis; and as targets of injury and agents of repair.