Regulation of natural killer cell-mediated swine endothelial cell lysis through genetic remodeling of a glycoantigen

The effect of remodeling of a glycoantigen such as the alpha-Gal epitope, G al alpha 1,3Gal beta 1, 4GlcNAc-R, by the introduction of glycosyltransfera se genes on natural killer (NK) cell-mediated direct cytotoxicity was inves tigated using human peripheral blood mononuclear cells (PBMC) or an NK-like cell line, YT cells, as an effector, and swine endothelial cells (SEC) as a target. Several SEC transfectants were established by transfection with t he genes for beta 1,4-N-acetylglucosaminyltransferase III, alpha 2,3-sialyl transferase and alpha 1,2-fucosyltransferase. These transfections led to dr amatic reductions in both direct and indirect NK cell-mediated cytotoxicity , by 72-94% in the case of PBMC and 27-72% in that of YT cells, in addition to an effective reduction in xenoantigenicity, which is substantially caus ed by the alpha-Gal epitope, to human natural antibodies. The NK cell-media ted direct cytotoxicity was remarkably blocked by an anti-alpha-Gal epitope monoclonal antibody or GSI lectin which preferentially binds to the epitop e. Furthermore, treatment of the parental cells with alpha-galactosidase re sulted in a significant reduction in cytotoxicity. These results suggest th at the alpha-Gal epitope is involved not only in hyperacute rejection and a cute vascular rejection, but also in NK cell-mediated direct cytotoxicity. Thus, the genetic remodeling of the alpha-Gal epitope and probably other gl ycoantigens as well can be expected to represent a new approach for overcom ing not only indirect but also direct immunity to xenografts.