title: HLA antibodies present in the sera of sensitized patients awaiting renal transplant are also reactive to swine leukocyte antigens.
abstract: BACKGROUND
  To determine whether preformed HLA alloantibodies present in the sera of patients awaiting kidney transplantation will be detrimental to a potential porcine xenograft, we tested their cross-reactivity to swine leukocyte antigens (SLA).
  
  
  METHODS
  Sera obtained from patients with varying levels of HLA sensitization (high panel-reactive antibodies > 70%, n= 7; moderate panel-reactive antibodies 30-40%, n=2) were analyzed. Pooled normal human AB sera and sera from nonsensitized patients (n=3) served as negative control. IgG was purified by protein-G chromatography, and xenoreactive natural antibodies (XNA) were depleted by passing the IgG through a series of melibiose and thyroglobulin-agarose columns. The elimination of XNA from HLA IgG preparations was confirmed by GS-IB4 lectin blocking assay and by an ELISA.
  
  
  RESULTS
  IgG isolated from normal AB serum and three nonsensitized patients, which was depleted of XNA (HLA-IgG), did not react to human or porcine lymphocytes (peripheral blood mononuclear cells; PBMC) either by flow cytometry or by complement-dependent microcytotoxicity assays. However, HLA-IgG isolated from nine sensitized patients were reactive to a panel of porcine peripheral blood lymphocytes (n=6) by flow cytometry (>50 mean channel shift) and in complement-dependent microcytotoxicity assays in addition to their reactivity to human PBMC. The binding of HLA-IgG to porcine PBMC was significantly reduced by preabsorption with pooled human platelet concentrate. Further, the HLA IgG showed recognition of 45-kDa affinity-purified SLA class I on Western blots.
  
  
  CONCLUSIONS
  This study demonstrates that HLA antibodies present in the sera of sensitized individuals can cross-react with SLA. Thus, xenotransplantation of porcine organs into HLA-sensitized patients has the potential to be rejected by humoral mechanisms. Testing to avoid such cross-reactive antibodies should be considered.
authors.affiliation: Department of Surgery, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
authors.forename: B
authors.initials: B
authors.lastname: Naziruddin
authors.forename: S
authors.initials: S
authors.lastname: Durriya
authors.forename: D
authors.initials: D
authors.lastname: Phelan
authors.forename: B F
authors.initials: BF
authors.lastname: Duffy
authors.forename: B
authors.initials: B
authors.lastname: Olack
authors.forename: D
authors.initials: D
authors.lastname: Smith
authors.forename: T
authors.initials: T
authors.lastname: Howard
authors.forename: T
authors.initials: T
authors.lastname: Mohanakumar
mesh_terms: D000818:Animals; D015153:Blotting, Western; D003429:Cross Reactions / Q000276:immunology; D005434:Flow Cytometry; D006680:HLA Antigens / Q000276:immunology*; D006801:Humans; D007114:Immunization; D007518:Isoantibodies / Q000032:analysis*; D016030:Kidney Transplantation / Q000276:immunology*; D009000:Monocytes / Q000276:immunology; D013552:Swine / Q000097:blood / Q000276:immunology*; D014183:Transplantation, Heterologous / Q000276:immunology*
chemical_list: D006680:HLA Antigens; D007518:Isoantibodies