title: Tolerance of allogeneic heart grafts in mice simultaneously reconstituted with purified allogeneic hematopoietic stem cells.
abstract: BACKGROUND
  Animals reconstituted with allogeneic whole bone marrow (WBM) are often tolerant of donor-specific solid organ grafts. Clinical application of bone marrow transplantation in solid organ transplantation has been limited, however, principally by graft-versus-host disease. We previously demonstrated that hematopoietic stem cells (HSCs) reconstitute lethally irradiated allogeneic mice without producing graft-versus-host disease. The purpose of this study was to determine whether tolerance to solid organ grafts could be induced in mice reconstituted with HSCs.
  
  
  METHODS
  BALB/c mice were lethally irradiated and reconstituted with allogeneic C57BL/Ka, Thy-1.1 WBM or HSCs. An isolated group was given a limited number of HSCs (250 cells) and a subpopulation of allogeneic cells known to facilitate HSC engraftment (facilitators). C57BL/Ka, Thy-1.1 neonatal heart grafts were placed in reconstituted animals either at the time of hematopoietic transplant or 35 days later. Third-party C3H grafts were placed over 2 months after hematopoietic reconstitution. Tolerance was defined as the persistence of cardiac contraction for the duration of evaluation (125-270 days).
  
  
  RESULTS
  All surviving mice that were reconstituted with C57BL/Ka, Thy-1.1 HSCs, WBM, or HSCs and facilitators were tolerant of C57BL/Ka grafts long-term. Third-party C3H grafts placed in reconstituted animals were rejected by day 12, whereas those placed in unmanipulated mice were rejected by day 9.
  
  
  CONCLUSIONS
  These data indicate that tolerance to concurrently or subsequently placed solid organ grafts can be reliably achieved with limited numbers of purified HSCs in a model where immunocompetence to third-party major histocompatibility complex antigens is delayed but intact.
authors.affiliation: Department of Pathology, Stanford University School of Medicine, California 94305, USA. kimberly@leland.stanford.edu
authors.forename: K L
authors.initials: KL
authors.lastname: Gandy
authors.forename: I L
authors.initials: IL
authors.lastname: Weissman
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D018414:CD8-Positive T-Lymphocytes / Q000166:cytology / Q000276:immunology; D005434:Flow Cytometry; D006084:Graft Rejection / Q000276:immunology; D006085:Graft Survival / Q000276:immunology*; D016027:Heart Transplantation / Q000276:immunology*; D018380:Hematopoietic Stem Cell Transplantation; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000276:immunology*; D016130:Immunophenotyping; D007165:Immunosuppression Therapy / Q000379:methods*; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D013997:Time Factors; D014184:Transplantation, Homologous