title: Xenogeneic thymokidney and thymic tissue transplantation in a pig-to-baboon model: I. Evidence for pig-specific T-cell unresponsiveness.
abstract: BACKGROUND
  The potential of xenotransplantation for clinical application will require overcoming barriers of humoral and cellular rejection, through strategies using immune suppression or tolerance induction. This laboratory has previously reported the induction of tolerance in the discordant xenogeneic model of pig-to-rodent thymic transplantation. We also have described a miniature swine model of fully mismatched allogeneic composite vascularized thymokidney transplantation that induced transplantation tolerance. We tested a combination of these approaches in a clinically relevant pig-to-primate model of xenotransplantation.
  
  
  METHODS
  Composite thymokidney grafts were prepared 40 to 80 days before transplantation by the autologous implantation of thymic tissue under the renal capsule of human decay-accelerating factor transgenic swine. Baboons received xenotransplants of both human decay-accelerating factor composite thymokidneys and omental implants of thymic tissue. Recipients were treated with an immunosuppressive-conditioning regimen including thymectomy or thymic irradiation, extracorporeal immunoadsorption of anti-alphaGal antibodies and T-cell depletion. Recipients were followed for indicators of xenograft rejection, T-cell depletion and reconstitution, anti-alphaGal antibody levels, and mixed lymphocyte responses. Immunologic responses were studied in those animals that survived for more than 3 weeks.
  
  
  RESULTS
  Thymokidney xenografts survived for up to 30 days, with evidence of viable thymic epithelium and Hassall's corpuscles under the renal capsule and in the omental implants, and with evidence of few host lymphocytes. Three animals demonstrated donor-specific unresponsiveness, while maintaining normal alloresponses, in mixed-lymphocyte-response assays performed after immunosuppression had been stopped. Rejected grafts demonstrated humoral damage without evidence of cellular infiltrates. After graftectomy, one animal maintained donor-specific cellular unresponsiveness and stable anti-alphaGal antibody levels for more than 2 months.
  
  
  CONCLUSIONS
  We concluded that composite thymokidney and thymic-tissue xenotransplantation from swine to baboons can induce donor-specific cellular unresponsiveness and stable anti-alphaGal antibody levels, suggesting avoidance of sensitization after xenotransplantation. The presence of viable donor-swine thymic epithelium could have a role in the development of donor-specific T-cell tolerance. Further strategies to address humoral rejection could prolong graft survival and result in long-term tolerance to xenografts.
authors.affiliation: Transplantation Biology Research Center, Massachusetts General Hospital/Harvard Medical School, Boston, MA, USA.
authors.forename: Rolf N
authors.initials: RN
authors.lastname: Barth
authors.forename: Shin
authors.initials: S
authors.lastname: Yamamoto
authors.forename: John C
authors.initials: JC
authors.lastname: LaMattina
authors.forename: Naoki
authors.initials: N
authors.lastname: Kumagai
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kitamura
authors.forename: Parsia A
authors.initials: PA
authors.lastname: Vagefi
authors.forename: Michel
authors.initials: M
authors.lastname: Awwad
authors.forename: Robert B
authors.initials: RB
authors.lastname: Colvin
authors.forename: David K C
authors.initials: DK
authors.lastname: Cooper
authors.forename: Megan
authors.initials: M
authors.lastname: Sykes
authors.forename: David H
authors.initials: DH
authors.lastname: Sachs
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Yamada
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified / Q000235:genetics; D000906:Antibodies / Q000032:analysis; D018958:CD55 Antigens / Q000235:genetics / Q000378:metabolism; D005260:Female; D005700:Galactosyltransferases / Q000276:immunology; D006084:Graft Rejection / Q000473:pathology; D006085:Graft Survival; D006801:Humans; D007668:Kidney / Q000473:pathology; D016030:Kidney Transplantation; D007959:Lymphocyte Culture Test, Mixed; D008297:Male; D009852:Omentum / Q000601:surgery; D010215:Papio; D013552:Swine / Q000235:genetics / Q000502:physiology; D013601:T-Lymphocytes / Q000502:physiology*; D013950:Thymus Gland / Q000473:pathology / Q000637:transplantation*; D023001:Transplantation Tolerance; D014183:Transplantation, Heterologous; D016042:Transplantation, Heterotopic
chemical_list: D000906:Antibodies; D018958:CD55 Antigens; D005700:Galactosyltransferases; C047006:N-acetyllactosaminide alpha-1,3-galactosyltransferase