title: Creation of chimeric hearts: a tool for testing the "passenger leukocyte" hypothesis.
abstract: BACKGROUND
  Bone marrow-derived antigen-presenting cells (APCs) are thought to be a migratory component of organ allografts that activate the rejection response, and recently they have been postulated to play a critical role in tolerance induction. Our goal was to create chimeric hearts (organs with parenchyma and APCs of differing genotype) for use in models of transplantation to test the "passenger leukocyte" theory.
  
  
  METHODS
  Murine bone marrow transplantation were performed in two fully major histocompatibility complex (MHC) mismatched strain combinations: C3H-->B10 and CBA-->BALB/c. Recipients were lethally irradiated (10 Gy) and then received 1 x 10(7) bone marrow cells intravenously. Bone marrow transplant survivors had their organ APCs isolated by digestion with collagenase D, followed by density gradient centrifugation. The APC-enriched fraction was stained with fluorescein-labeled monoclonal antibodies specific for either donor (I-Ak) or recipient (I-Ab/d) class II MHC antigens, which are expressed by all APCs but not by parenchymal cells. Donor and recipient class II expression was determined by flow cytometry.
  
  
  RESULTS
  Sixty-nine of 100 (69.0%) of C3H-->B10 and 52/107 (48.6%) of CBA-->BALB/c bone marrow transplant recipients survived more than 100 days, whereas all B10 (n = 12) and BALB/c (n = 10) irradiation controls died within 14 days. Mortality appeared to be caused by engraftment failure as most recipients died before day 20. Flow cytometry demonstrated complete APC replacement in hearts (n = 17) and spleens (n = 40), as APC-enriched fractions stained only for donor class II MHC antigens.
  
  
  CONCLUSIONS
  Bone marrow transplantation leads to replacement of heart APCs in two murine models. Chimeric hearts are now being used to test the role of APCs in allograft rejection and in tolerance induction.
authors.affiliation: Division of Cardiothoracic Surgery, University of Pennsylvania Health System, Philadelphia 19104, USA.
authors.forename: S D
authors.initials: SD
authors.lastname: Eiref
authors.forename: W
authors.initials: W
authors.lastname: Zhang
authors.forename: S H
authors.initials: SH
authors.lastname: Popma
authors.forename: L J
authors.initials: LJ
authors.lastname: Shah
authors.forename: J S
authors.initials: JS
authors.lastname: Moore
authors.forename: B R
authors.initials: BR
authors.lastname: Rosengard
mesh_terms: D000818:Animals; D000938:Antigen-Presenting Cells / Q000276:immunology; D001853:Bone Marrow / Q000276:immunology; D016026:Bone Marrow Transplantation / Q000276:immunology; D002423:Cause of Death; D002465:Cell Movement; D002499:Centrifugation, Density Gradient; D002678:Chimera / Q000276:immunology*; D017364:Collagenases; D004195:Disease Models, Animal; D005434:Flow Cytometry; D005452:Fluoresceins; D005456:Fluorescent Dyes; D005838:Genotype; D006084:Graft Rejection / Q000276:immunology; D006085:Graft Survival; D000949:Histocompatibility Antigens Class II / Q000032:analysis; D007108:Immune Tolerance / Q000276:immunology; D007962:Leukocytes / Q000276:immunology*; D008285:Major Histocompatibility Complex / Q000276:immunology; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D008808:Mice, Inbred CBA; D008815:Mice, Inbred Strains; D009206:Myocardium / Q000276:immunology; D013154:Spleen / Q000276:immunology; D015996:Survival Rate; D019172:Transplantation Conditioning; D014184:Transplantation, Homologous / Q000276:immunology; D014916:Whole-Body Irradiation
chemical_list: D005452:Fluoresceins; D005456:Fluorescent Dyes; D000949:Histocompatibility Antigens Class II; D017364:Collagenases