title: Evidence that FoxP3+ regulatory T cells may play a role in promoting long-term acceptance of composite tissue allotransplants.
abstract: BACKGROUND
  FoxP3/CD4/CD25 regulatory T cells (Treg) play an important role in maintaining peripheral tolerance and are potent suppressors of T-cell activation. In this study, we evaluated the role of Treg in peripheral tolerance to composite tissue allografts (CTA).
  
  
  METHODS
  Mixed allogeneic chimeric rats were prepared by preconditioning recipients with anti-αβ-T-cell receptor monoclonal antibody followed by total body irradiation. Animals received T-cell-depleted August Copenhagen Irish bone marrow cells followed by antilymphocyte serum and FK-506. A modified osteomyocutaneous hindlimb flap composed of bone and all limb tissue components was placed in animals with chimerism greater than or equal to 1% on day 28. Recipients with CTA surviving more than or equal to 6 months were evaluated for Treg. Skin samples from tolerant long-term allogeneic transplanted, syngeneic transplanted, rejected, and naïve animals were immunostained with fluorochrome-conjugated anti-FoxP3 and anti-CD4 monoclonal antibody and visualized under a laser confocal microscope.
  
  
  RESULTS
  Significant CD4/FoxP3 Treg infiltrates were observed in tolerant donor-allograft skin samples. No graft infiltrating FoxP3 cells were observed in rejector, naïve, or skin from syngeneic CTA. In parallel experiments, mixed leukocyte reaction assays were performed to investigate the suppressor function of Treg cells. Splenocytes from tolerant, rejected, and naïve rats were sorted by flow cytometry for CD4/CD25 T cells. Treg demonstrated similar suppressive levels between the three groups.
  
  
  CONCLUSIONS
  These data suggest that Treg may play an important role in maintenance of tolerance and promoting graft acceptance in long-term CTA acceptors and may explain the favorable outcomes observed in clinical CTA recipients.
authors.affiliation: Regenerex, LLC, Louisville, KY, USA.
authors.forename: Larry D
authors.initials: LD
authors.lastname: Bozulic
authors.forename: Yujie
authors.initials: Y
authors.lastname: Wen
authors.forename: Hong
authors.initials: H
authors.lastname: Xu
authors.forename: Suzanne T
authors.initials: ST
authors.lastname: Ildstad
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D018920:Coculture Techniques; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D051858:Forkhead Transcription Factors / Q000097:blood / Q000378:metabolism*; D006084:Graft Rejection / Q000276:immunology* / Q000517:prevention & control; D006085:Graft Survival / Q000187:drug effects; D006614:Hindlimb / Q000637:transplantation*; D007166:Immunosuppressive Agents / Q000494:pharmacology; D007959:Lymphocyte Culture Test, Mixed; D008297:Male; D018613:Microscopy, Confocal; D051381:Rats; D011916:Rats, Inbred F344; D011920:Rats, Inbred WF; D016038:Skin Transplantation / Q000276:immunology*; D013154:Spleen / Q000276:immunology; D013524:Surgical Flaps / Q000276:immunology*; D050378:T-Lymphocytes, Regulatory / Q000187:drug effects / Q000276:immunology*; D013997:Time Factors; D018183:Transplantation Chimera; D019172:Transplantation Conditioning; D023001:Transplantation Tolerance / Q000187:drug effects; D014184:Transplantation, Homologous; D014916:Whole-Body Irradiation
chemical_list: D051858:Forkhead Transcription Factors; C500522:Foxp3 protein, rat; D007166:Immunosuppressive Agents