title: Antigen expression in xenotransplantation: how low must it go?
abstract: BACKGROUND
  Acute vascular rejection (AVR) is an important immunological barrier to xenotransplantation. Thought to be initiated by xenoreactive antibodies, acute vascular rejection might, in principle, be avoided by engineering animals to express low levels of antigen. The extent to which antigen expression would have to be decreased to achieve such a goal is unknown.
  
  
  METHODS
  We estimated the decrease in expression of a xenogeneic antigen, Galalpha1-3Gal, which might be needed to avert acute vascular rejection of xenotransplants based on the decrease in antibody binding to endothelium that would prevent tissue damage.
  
  
  RESULTS
  The level of decrease needed in Galalpha1-3Gal expression needed to avoid acute vascular rejection was estimated to exceed 96% of baseline. The extent of the decrease needed reflected, in part, a substantial "excess" of Galalpha1-3Gal on porcine endothelial cell surfaces.
  
  
  CONCLUSIONS
  Although the change in antigen expression required to avoid acute vascular rejection might be conditioned by various factors, the very large magnitude of this change necessitates application of highly efficient approaches to antigen modification.
authors.affiliation: Department of Surgery, Duke University Medical Center, Durham, NC 27710, USA.
authors.forename: W
authors.initials: W
authors.lastname: Parker
authors.forename: S S
authors.initials: SS
authors.lastname: Lin
authors.forename: J L
authors.initials: JL
authors.lastname: Platt
mesh_terms: D000818:Animals; D015478:Antigens, Heterophile / Q000096:biosynthesis*; D004187:Disaccharides / Q000276:immunology; D004730:Endothelium, Vascular / Q000637:transplantation; D006084:Graft Rejection / Q000517:prevention & control; D010215:Papio; D013552:Swine; D014183:Transplantation, Heterologous / Q000276:immunology
chemical_list: D015478:Antigens, Heterophile; D004187:Disaccharides; C055075:galactosyl-(1-3)galactose