Preventing human CD8+ cytotoxic T lymphocyte-mediated cytotoxicity against swine endothelial cells by overexpression of human decoy Fas antigen.
Although the birth of homozygous alpha1, 3 galactosyltransferase gene-knockout pigs raised hopes for an imminent breakthrough in the prevention in the antibody-mediated rejection of pig to human discordant xenotransplants, human CD8(+) cytotoxic T lymphocyte (CTL)-mediated killing may represent a new immunological barrier to long-term survival in xenograft recipients. In this study, we demonstrated that the cytotoxicity of human CD8(+) CTL against swine endothelial cells (SEC) is highly detrimental and mediated at least in part by the Fas/FasL pathway. To prevent this CTL-mediated xenocytotoxicity, we overexpressed the human decoy Fas antigen, which does not contain a death domain in its cytoplasmic region, by means of binding competition with endogenous pig Fas antigen on SEC for the common ligand, human FasL. Furthermore, we generated a membrane-bound form of human FasL that cannot be cleaved by a putative metalloproteinase to produce a soluble form, which was assessed as an inhibitor of CTL cytotoxicity. Both human decoy Fas and membrane-bound FasL were effective to prevent CTL-mediated killing, suggesting that these novel molecules may represent a step forward toward preventing CD8(+) CTL-mediated xenograft rejection. The combined expression of both molecules may be more beneficial to protect xenograft cells.
Kawamoto
K
K
Department of Surgery (E1), Osaka University Graduate School of Medicine, Osaka, Japan.
Tanemura
M
M
Ito
T
T
Uchikoshi
F
F
Shimada
K
K
Nishida
T
T
Matsuda
H
H
D000818:Animals; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology*; D004730:Endothelium, Vascular / Q000276:immunology / Q000637:transplantation*; D005700:Galactosyltransferases / Q000172:deficiency / Q000235:genetics; D017353:Gene Deletion; D006801:Humans; D013552:Swine; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology*; D014183:Transplantation, Heterologous; D019014:fas Receptor / Q000235:genetics*
D019014:fas Receptor; D005700:Galactosyltransferases