title: Terminal sialic acid residues on human glycophorin A are recognized by porcine kupffer cells.
abstract: BACKGROUND
  We have previously shown that recognition of human erythrocytes by porcine Kupffer cells is mediated by a carbohydrate-dependent mechanism. The present study explores the possible ligands existing on human glycophorin A and tests their ability to inhibit erythrocyte rosette formation.
  
  
  METHODS
  Human erythrocytes were tested for ABO and MN specificity and used as targets in a 51Chromium quantitative erythrocyte rosette assay. Monosaccharides present on human glycophorin A, neuraminyl lactoses, bovine and porcine submaxillary mucins (BSM and PSM), and hyaluronic acid as well as proteoglycan N-linked glycosidase F(PNGaseF)- and sialidase A-treated human erythrocyte glycoproteins (hEGP) and human erythrocytes were all tested for inhibitory potential in the rosetting assay.
  
  
  RESULTS
  Porcine Kupffer-cell recognition of human erythrocytes was insensitive to differences in blood groups A, B, O, or MN. At 30 mM, the monosaccharide, N-acetylneuraminic acid, and the trisaccharide mixture, neuraminyl lactoses, disrupted human erythrocyte recognition by 25% and 30%, respectively. A dilution of BSM but not PSM inhibited the rosetting assay by 17% (.2 mg/mL), 33% (1 mg/mL), and 53% (2 mg/mL). The same dilution of hyaluronic acid had no effect on rosetting. Removal of N-linked oligosaccharides from hEGP with PNGaseF did not impair its ability to inhibit the rosetting assay. In contrast, removal of sialic acid completely abrogated its inhibitory ability. Treatment of whole human erythrocytes with sialidase A likewise prevented recognition by porcine Kupffer cells.
  
  
  CONCLUSIONS
  Terminal sialic acid on human erythrocytes is a target recognized by porcine Kupffer cells, suggesting a role for a sialic-acid receptor in innate cellular recognition of xenogeneic epitopes. Inasmuch as this work reveals a carbohydrate-recognition mechanism for cellular rejection, we shed light on a potential new boundary that will need to be overcome within xenotransplantation.
authors.affiliation: Department of Urology, Medical College of Ohio, Toledo, OH, USA. Cburlak@niaid.nih.gov
authors.forename: Christopher
authors.initials: C
authors.lastname: Burlak
authors.forename: Lisa M
authors.initials: LM
authors.lastname: Twining
authors.forename: Michael A
authors.initials: MA
authors.lastname: Rees
mesh_terms: D000017:ABO Blood-Group System; D000818:Animals; D002241:Carbohydrates / Q000737:chemistry; D002417:Cattle; D004305:Dose-Response Relationship, Drug; D004912:Erythrocytes / Q000378:metabolism; D006021:Glycophorins / Q000737:chemistry*; D006023:Glycoproteins / Q000737:chemistry; D006084:Graft Rejection; D006801:Humans; D006820:Hyaluronic Acid / Q000737:chemistry; D007728:Kupffer Cells / Q000166:cytology / Q000378:metabolism*; D007785:Lactose / Q000737:chemistry; D009005:Monosaccharides / Q000737:chemistry; D009077:Mucins / Q000737:chemistry; D019158:N-Acetylneuraminic Acid / Q000737:chemistry* / Q000378:metabolism; D009439:Neuraminidase / Q000737:chemistry; D043524:Peptide-N4-(N-acetyl-beta-glucosaminyl) Asparagine Amidase / Q000737:chemistry; D011485:Protein Binding; D013045:Species Specificity; D013552:Swine; D014183:Transplantation, Heterologous / Q000379:methods*
chemical_list: D000017:ABO Blood-Group System; D002241:Carbohydrates; D006021:Glycophorins; D006023:Glycoproteins; D009005:Monosaccharides; D009077:Mucins; D006820:Hyaluronic Acid; D009439:Neuraminidase; D043524:Peptide-N4-(N-acetyl-beta-glucosaminyl) Asparagine Amidase; D019158:N-Acetylneuraminic Acid; D007785:Lactose