title: Blockade of the CD40/CD154 pathway enhances T-cell-depleted allogeneic bone marrow engraftment under nonmyeloablative and irradiation-free conditioning therapy.
abstract: BACKGROUND
  T-cell-depleted bone marrow transplantation (TDBMT) can prevent graft-versus-host disease (GvHD). However, depleting T cells from allogeneic bone marrow often results in failure of bone marrow engraftment under irradiation conditioning. It is not know whether donor T cells are essential for bone marrow engraftment and whether blocking the CD40/CD154 pathway promotes allogeneic TDBM engraftment under nonmyeloablative and irradiation-free fludarabine phosphate and cyclophosphamide conditioning therapy.
  
  
  METHODS
  Using fully major histocompatibility complex (MHC)-matched mouse models, we investigated whether donor T cells are essential for bone marrow engraftment under fludarabine phosphate and cyclophosphamide conditioning therapy. We also determined whether the barrier of allogeneic TDBM could be overcome by blocking the CD40/CD154 pathway. Donor chimerism was detected by flow cytometric analysis. Donor-specific tolerance through establishing mixed chimerism was tested in vivo by skin transplantation and in vitro by mixed leukocyte reaction and enzyme-linked immunospot (ELISPOT) assay.
  
  
  RESULTS
  Compared with unmodified bone marrow, TDBM resulted in poor engraftment when fully MHC-mismatched donors were used. However, anti-CD154 monoclonal antibody (mAb) treatment significantly enhanced donor TDBM engraftment. TDBM engraftment was also seen in CD154 knockout mice. A stable and high level of multilinage donor chimerism was achieved. Recovery of host CD3 T cells was suppressed, and recovery of donor CD3 T cells was promoted, after TDBMT and anti-CD154 mAb treatment. Donor chimerism was established by TDBMT induced donor-specific tolerance in vivo and in vitro.
  
  
  CONCLUSIONS
  Donor T cells facilitate bone marrow engraftment under nonmyeloablative and irradiation-free conditioning therapy, and the blocking the CD40/CD154 pathway can replace donor T cells to promote TDBM engraftment.
authors.affiliation: Department of Surgery and Diabetes, Institute for Immunology and Transplantation, University of Minnesota, Minneapolis, MN 55455, USA.
authors.forename: Yisheng
authors.initials: Y
authors.lastname: Pan
authors.forename: Bin
authors.initials: B
authors.lastname: Luo
authors.forename: Haken
authors.initials: H
authors.lastname: Sozen
authors.forename: Hannes
authors.initials: H
authors.lastname: Kalscheuer
authors.forename: Bruce R
authors.initials: BR
authors.lastname: Blazar
authors.forename: David E R
authors.initials: DE
authors.lastname: Sutherland
authors.forename: Benhard J
authors.initials: BJ
authors.lastname: Hering
authors.forename: Zhiguang
authors.initials: Z
authors.lastname: Guo
mesh_terms: D000818:Animals; D016025:Bone Transplantation / Q000276:immunology / Q000379:methods*; D019013:CD40 Antigens / Q000276:immunology*; D023201:CD40 Ligand / Q000276:immunology*; D003520:Cyclophosphamide / Q000494:pharmacology; D006086:Graft vs Host Disease / Q000517:prevention & control; D006650:Histocompatibility Testing; D007166:Immunosuppressive Agents / Q000494:pharmacology; D007959:Lymphocyte Culture Test, Mixed; D008212:Lymphocyte Depletion; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008809:Mice, Inbred C3H; D023421:Models, Animal; D016038:Skin Transplantation / Q000276:immunology*; D013601:T-Lymphocytes / Q000187:drug effects / Q000276:immunology*; D018183:Transplantation Chimera; D014184:Transplantation, Homologous
chemical_list: D019013:CD40 Antigens; D007166:Immunosuppressive Agents; D023201:CD40 Ligand; D003520:Cyclophosphamide