Prevention of diabetes in nonobese diabetic mice by nonmyeloablative allogeneic bone marrow transplantation

Objective Autoimmune diabetes in nonobese diabetic (NOD) mice can be prevented by allogeneic bone marrow transplantation (BMT) from diabetes-resistant murine strains. Donor-specific tolerance can also be induced by BMT; however, clinical application of nonmyeloablative conditioning prior to BMT may be essential for reducing transplant-related toxicity and mortality. In this study, we have attempted to treat autoimmunity using a new nonmyeloablative regimen for BMT. Materials and methods Naïve NOD were irradiated with 650 cGy and injected intravenously (IV) with splenocytes from overtly diabetic NOD mice for induction of diabetes mellitus. Three days later, experimental mice received allogeneic C57BL/6 or (C57BL/6 × BALB/c) F1 bone marrow (BM) cells IV for intentional activation of donor-reactive cells, and 24 hours later intraperitoneal injection of cyclophosphamide (CY) for selective depletion of alloreactive cells. In order to induce chimerism, recipients were given a second IV inoculum of donor BM 1 day after CY. Results Our method of nonmyeloablative BMT converted recipients to full or to mixed chimeras and prevented development of diabetes. Although NOD mice treated with 200 mg/kg CY died of graft-vs-host disease (GVHD), we observed diabetes-free survival for >300 days in 90% of C57BL/6 → NOD BM chimeras treated with 60 mg/kg CY. Conclusion Our data show that allogeneic BMT after reduced-intensity conditioning based on deletion of activated donor-reactive host cells by means low-dose CY results in prevention of autoimmune diabetes by converting recipients to stable, GVHD-free BM chimeras.