title: Lack of galactose-alpha-1,3-galactose expression on porcine endothelial cells prevents complement-induced lysis but not direct xenogeneic NK cytotoxicity.
abstract: The galactose-alpha-1,3-galactose (alphaGal) carbohydrate epitope is expressed on porcine, but not human cells, and therefore represents a major target for preformed human anti-pig natural Abs (NAb). Based on results from pig-to-primate animal models, NAb binding to porcine endothelial cells will likely induce complement activation, lysis, and hyperacute rejection in pig-to-human xenotransplantation. Human NK cells may also contribute to innate immune responses against xenografts, either by direct recognition of activating molecules on target cells or by FcgammaRIII-mediated xenogeneic Ab-dependent cellular cytotoxicity (ADCC). The present study addressed the question as to whether the lack of alphaGal protects porcine endothelial cells from NAb/complement-induced lysis, direct xenogeneic NK lysis, NAb-dependent ADCC, and adhesion of human NK cells under shear stress. Homologous recombination, panning, and limiting dilution cloning were used to generate an alphaGal-negative porcine endothelial cell line, PED2*3.51. NAb/complement-induced xenogeneic lysis of PED2*3.51 was reduced by an average of 86% compared with the alphaGal-positive phenotype. PED2*3.51 resisted NK cell-mediated ADCC with a reduction of lysis ranging from 30 to 70%. However, direct xenogeneic lysis of PED2*3.51, mediated either by freshly isolated or IL-2-activated human NK cells or the NK cell line NK92, was not reduced. Furthermore, adhesion of IL-2-activated human NK cells did not rely on alphaGal expression. In conclusion, removal of alphaGal leads to a clear reduction in complement-induced lysis and ADCC, but does not resolve adhesion of NK cells and direct anti-porcine NK cytotoxicity, indicating that alphaGal is not a dominant target for direct human NK cytotoxicity against porcine cells.
authors.affiliation: Department of Internal Medicine, Laboratory for Transplantation Immunology, University Hospital, Zurich, Switzerland.
authors.forename: Bettina C
authors.initials: BC
authors.lastname: Baumann
authors.forename: Pietro
authors.initials: P
authors.lastname: Forte
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Hawley
authors.forename: Robert
authors.initials: R
authors.lastname: Rieben
authors.forename: Mårten K J
authors.initials: MK
authors.lastname: Schneider
authors.forename: Jörg D
authors.initials: JD
authors.lastname: Seebach
mesh_terms: D000818:Animals; D000910:Antibodies, Heterophile / Q000378:metabolism; D000920:Antibody-Dependent Cell Cytotoxicity / Q000235:genetics; D015478:Antigens, Heterophile / Q000276:immunology / Q000502:physiology*; D001666:Binding Sites, Antibody / Q000235:genetics; D002448:Cell Adhesion / Q000235:genetics / Q000276:immunology; D002460:Cell Line; D002461:Cell Line, Transformed; D002999:Clone Cells; D003165:Complement System Proteins / Q000502:physiology*; D003602:Cytotoxicity, Immunologic / Q000235:genetics; D004187:Disaccharides / Q000172:deficiency* / Q000235:genetics* / Q000276:immunology; D004730:Endothelium, Vascular / Q000166:cytology / Q000276:immunology* / Q000378:metabolism*; D006801:Humans; D007108:Immune Tolerance / Q000235:genetics; D007694:Killer Cells, Natural / Q000276:immunology*; D013314:Stress, Mechanical; D013552:Swine
chemical_list: D000910:Antibodies, Heterophile; D015478:Antigens, Heterophile; D004187:Disaccharides; C055075:galactosyl-(1-3)galactose; D003165:Complement System Proteins