title: Characterization of porcine UL16-binding protein 1 endothelial cell surface expression.
abstract: BACKGROUND
  Natural killer (NK) cells participate in the immune response against solid organ allo- and xenografts and are tightly regulated through signals mediated by inhibiting and activating receptors expressed on their cell surface. Human NK cytotoxicity against porcine endothelial cells (pEC) is mediated by the interaction of the activating human NK receptor hNKG2D and its corresponding ligand on pEC, porcine UL-16 binding protein 1 (pULBP1). The aim of the present study was to characterize the regulation of pULBP1 cell-surface expression on primary porcine aortic endothelial cells (PAEC).
  
  
  METHODS
  A monoclonal antibody (mAb; aE5-63) directed against pULBP1 was generated by immunizing C57BL/6 mice with the pEC line PEDSV.15, and used in cellular ELISA to determine pULBP1 cell surface expression. PAEC were either left untreated or stimulated with human or porcine cytokines [interferon gamma (IFN-gamma), tumor necrosis factor alpha (TNF-alpha)], human serum, cultured under hypoxic conditions, or infected with human or porcine cytomegalovirus (CMV).
  
  
  RESULTS
  Neither human nor porcine IFN-gamma stimulation changed pULBP1 expression, whereas both human and porcine TNF-alpha stimulation as well as human and porcine CMV infection significantly decreased pULBP1 expression on PAEC. Coculture of PAEC with human serum strongly increased pULBP1 expression depending on the binding of human anti-pig antibodies. Exposure of PAEC to hypoxia only slightly increased pULBP1 expression.
  
  
  CONCLUSIONS
  In conclusion, (i) the novel anti-pULBP1 IgM mAb aE5-63 represents a useful tool to study pULBP1/hNKG2D-mediated responses in xenotransplantation, and (ii) the expression of pULBP1, a human-pig cross-species functional hNKG2D ligand, on the surface of PAEC is modulated by various stimuli associated with transplantation.
authors.affiliation: Department of Internal Medicine, Laboratory for Transplantation Immunology, University Hospital Zurich, Zurich, Switzerland.
authors.forename: Benjamin G
authors.initials: BG
authors.lastname: Lilienfeld
authors.forename: Anita
authors.initials: A
authors.lastname: Schildknecht
authors.forename: Lukas L
authors.initials: LL
authors.lastname: Imbach
authors.forename: Nicolas J
authors.initials: NJ
authors.lastname: Mueller
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; D000911:Antibodies, Monoclonal / Q000276:immunology; D001011:Aorta / Q000166:cytology; D002352:Carrier Proteins / Q000276:immunology / Q000378:metabolism*; D015687:Cell Hypoxia; D002462:Cell Membrane / Q000378:metabolism*; D002478:Cells, Cultured; D017077:Culture Media, Conditioned; D042783:Endothelial Cells / Q000187:drug effects / Q000378:metabolism*; D015395:Histocompatibility Antigens Class I / Q000276:immunology / Q000378:metabolism*; D006801:Humans; D051379:Mice; D044967:Serum; D013552:Swine; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
chemical_list: D000911:Antibodies, Monoclonal; D002352:Carrier Proteins; D017077:Culture Media, Conditioned; D015395:Histocompatibility Antigens Class I; D014409:Tumor Necrosis Factor-alpha