title: CD40 ligand-specific antibodies synergize with cyclophosphamide to promote long-term transplantation tolerance across MHC barriers but inhibit graft-vs-leukemia effects of transplanted cells.
abstract: OBJECTIVE
  We previously demonstrated that allogeneic bone marrow transplantation (BMT) after low-dose total lymphoid irradiation (200 cGy) and depletion of donor-reactive cells with cyclophosphamide (Cy) converted recipients to graft-vs-host disease (GVHD)-free chimeras tolerant to donor skin grafts. BMT also generated strong graft-vs-leukemia (GVL) response. However, clinical application of the protocol was hampered by the requirement for a relatively high dose of Cy (200 mg/kg). In this study we have tried to minimize the Cy dose by a concomitant blockade of CD40-CD40L interaction.
  
  
  METHODS
  Mildly irradiated BALB/c mice were primed with C57BL/6 BM cells (BM(1)) and skin graft on day 0, injected with Cy (200 mg/kg or less) on day 1, and transplanted with a second C57BL/6 BM cell inoculum (BM(2)) on day 2. CD40L-specific antibody (MR1) was given with BM(1), BM(2), and 2 days later. Treated animals were monitored for survival, chimerism, and skin allograft rejection. The GVL potential of transplanted cells was examined in mice inoculated with BCL1 leukemia cells before irradiation.
  
  
  RESULTS
  Blocking CD40-CD40L interaction with MR1 mAb allowed the reduction of a tolerance-generating Cy dose by 50%. Unfortunately, adding MR1 to the protocol reduced the GVL potential of the transplanted cells. Neither low-dose Cy nor antibodies alone could downregulate donor or recipient immune response.
  
  
  CONCLUSIONS
  CD40L-specific antibodies synergize with Cy to induce bilateral transplantation tolerance. Therefore, their use may be beneficial for safer allogeneic BMT for nonmalignant indications. However, due to MR1-associated reduction of GVL effects, MR1 should be considered with caution as conditioning for BMT for leukemia-bearing recipients.
authors.affiliation: Department of Bone Marrow Transplantation and Cancer Immunotherapy, Hadassah University Hospital, Jerusalem, Israel
authors.forename: Tatyana B
authors.initials: TB
authors.lastname: Prigozhina
authors.forename: Olga
authors.initials: O
authors.lastname: Gurevitch
authors.forename: Gregory
authors.initials: G
authors.lastname: Elkin
authors.forename: Shoshana
authors.initials: S
authors.lastname: Morecki
authors.forename: Elena
authors.initials: E
authors.lastname: Yakovlev
authors.forename: Shimon
authors.initials: S
authors.lastname: Slavin
mesh_terms: D000069594:Abatacept; D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology*; D016026:Bone Marrow Transplantation; D019013:CD40 Antigens / Q000276:immunology; D023201:CD40 Ligand / Q000276:immunology*; D003520:Cyclophosphamide / Q000494:pharmacology*; D004357:Drug Synergism; D006082:Graft Enhancement, Immunologic; D020544:Graft vs Leukemia Effect / Q000187:drug effects*; D018796:Immunoconjugates / Q000494:pharmacology / Q000627:therapeutic use; D007166:Immunosuppressive Agents / Q000494:pharmacology* / Q000627:therapeutic use; D008212:Lymphocyte Depletion / Q000379:methods*; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D011828:Radiation Chimera; D012449:Safety; D016038:Skin Transplantation; D014184:Transplantation, Homologous / Q000276:immunology
chemical_list: D000911:Antibodies, Monoclonal; D019013:CD40 Antigens; D018796:Immunoconjugates; D007166:Immunosuppressive Agents; D023201:CD40 Ligand; D000069594:Abatacept; D003520:Cyclophosphamide