| Abstract: | MHC class II antigens play a crucial role in immunological responses. The expression of MHC class II antigens on monocytes and endothelial cells is reported to be variable and able to be induced by gamma-interferon. In this study we report on MHC class II antigen expression in vitro by arterial and venous canine endothelial cells, as detected with FACS analysis and indirect immunofluorescence with a monoclonal antibody against canine MHC class II antigens. It appears that cultured endothelial cells do not express MHC class II antigens. Their expression could be induced during a three-day incubation period in lymphokine-containing supernatant produced in mixed leukocyte culture (MLC). Cyclosporine (CsA) added to allogeneically stimulated or unstimulated canine lymphocytes in MLC inhibited the induction of expression by the MLC supernatant. The addition of CsA to MLC supernatant did not have an inhibitory effect. It is concluded that CsA inhibits the production of an MHC class-II-antigen-inducing lymphokine produced by lymphocytes in mixed cultures; allogeneic stimulation is not necessary for production of the lymphokine. It is postulated that a possible mode of action of CsA in prolongation of allograft survival is based on prevention of the induction of MHC class II antigen expression by endothelial cells. |
