Alloantigen presentation by canine endothelial cells. Presentation of autologous alloantigens in vitro.

Presentation of autologous alloantigen by certain cells in an allograft can result in allograft rejection. The precise type of cell in a graft responsible for this aspect of allograft rejection remains to be established. Here we report the capacity of canine venous endothelial cells to activate, in vitro, allogeneic lymphocytes for proliferation and differentiation by presentation of alloantigen. Antigen-presenting cell (APC)-depleted lymphocyte populations, prepared in a multistep procedure and tested for absence of APC, were cocultured with allogeneic venous endothelial cells. Proliferation and differentiation into cytotoxic T lymphocytes were measured. While mixed lymphocyte culture of APC-depleted lymphocytes did not result in proliferation and differentiation, coculture of allogeneic APC-depleted lymphocytes with venous endothelial cells resulted in proliferation and generation of cell-mediated cytotoxicity in these cultures. It is concluded that canine venous endothelial cells in vitro have the capacity to present alloantigen. The data suggest an essential role for endothelium in the initial phase of allograft rejection.