title: Simultaneous bone marrow and composite tissue transplantation in rats treated with nonmyeloablative conditioning promotes tolerance.
abstract: BACKGROUND
  Approaches to safely induce tolerance in vascularized composite allotransplantation (VCA) with chimerism through bone marrow transplantation (BMT) are currently being pursued. However, VCA was historically performed sequentially after donor chimerism was established. Delayed VCA is not clinically applicable due to the time constraints associated with procurement from deceased donors. A more clinically relevant approach to perform both BMT and VCA simultaneously was evaluated.
  
  
  METHODS
  Wistar Furth (RT1A) rats were treated with a short course of immunosuppressive therapy (anti-αβ-TCR monoclonal antibody, FK-506, and anti-lymphocyte serum). One day before BMT, rats were treated with varying doses of total body irradiation (TBI) followed by transplantation of heterotopic osteomyocutaneous flaps from hindlimbs of August Copenhagen Irish (RT1A) rats.
  
  
  RESULTS
  Eighty percent of rats conditioned with 300 cGy TBI and 40% of rats receiving 400 cGy TBI accepted the VCA. Mixed chimerism was detected in peripheral blood at 1 month after VCA, but chimerism was lost in all transplant recipients by 4 months. Most peripheral donor cells originated from the BMT and not from the VCA. Acceptors of VCA were tolerant of a donor skin graft challenge and no anti-donor antibodies were detectable, suggesting a central deletional mechanism for tolerance. Regulatory T cells (Treg) from spleens of acceptors more potently suppressed lymphocyte proliferation than Treg from rejectors in the presence of donor stimulator cells.
  
  
  CONCLUSIONS
  These studies suggest that simultaneous BMT and VCA may establish indefinite allograft survival in rats through Treg-mediated suppression and thymic deletion of alloreactive T cells.
authors.affiliation: Institute for Cellular Therapeutics, University of Louisville, Louisville, KY 40202-1760, USA.
authors.forename: Hong
authors.initials: H
authors.lastname: Xu
authors.forename: Deborah M
authors.initials: DM
authors.lastname: Ramsey
authors.forename: Shengli
authors.initials: S
authors.lastname: Wu
authors.forename: Larry D
authors.initials: LD
authors.lastname: Bozulic
authors.forename: Suzanne T
authors.initials: ST
authors.lastname: Ildstad
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000008:administration & dosage; D000961:Antilymphocyte Serum / Q000008:administration & dosage; D016026:Bone Marrow Transplantation / Q000276:immunology*; D049109:Cell Proliferation; D004307:Dose-Response Relationship, Radiation; D004359:Drug Therapy, Combination; D058752:Free Tissue Flaps / Q000098:blood supply* / Q000276:immunology / Q000637:transplantation*; D006084:Graft Rejection / Q000276:immunology / Q000517:prevention & control*; D006085:Graft Survival; D007166:Immunosuppressive Agents / Q000008:administration & dosage; D007519:Isoantigens / Q000276:immunology; D008213:Lymphocyte Activation; D008297:Male; D051381:Rats; D011912:Rats, Inbred ACI; D011920:Rats, Inbred WF; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000276:immunology; D016038:Skin Transplantation / Q000276:immunology*; D050378:T-Lymphocytes, Regulatory / Q000276:immunology; D016559:Tacrolimus / Q000008:administration & dosage; D013997:Time Factors; D018183:Transplantation Chimera; D019172:Transplantation Conditioning / Q000379:methods*; D023001:Transplantation Tolerance; D014916:Whole-Body Irradiation
chemical_list: D000911:Antibodies, Monoclonal; D000961:Antilymphocyte Serum; D007166:Immunosuppressive Agents; D007519:Isoantigens; D016693:Receptors, Antigen, T-Cell, alpha-beta; D016559:Tacrolimus