Long-Term Tolerance to Kidney Allografts After Induced Rejection of Donor Hematopoietic Chimerism in a Preclinical Canine Model.

Abstract 2991

Allogeneic hematopoietic cell transplantation provides a reliable method for inducing tolerance towards solid organ grafts. However, this procedure can result in graft-versus-host disease (GVHD) thereby limiting its application. Here we test the hypothesis that mixed chimerism can be intentionally reverted to host hematopoiesis without rejection of a kidney graft. Recipient dogs were given 2 Gy total body irradiation (TBI) before and a short course of immunosuppression after marrow infusion from dog leukocyte antigen-identical littermates. All dogs achieved stable mixed chimerism. After a mean of 20 weeks, one cohort of dogs received kidney transplants from their respective marrow donors. Subsequently, recipients were reconditioned with 2 Gy TBI and given autologous granulocyte-colony stimulating factor-mobilized leukocytes (recipient leukocyte infusion) that had been collected before marrow transplant. Dogs receiving a second TBI and recipient leukocyte infusion without a kidney transplant rejected their donor hematopoietic graft within 3 weeks. Dogs that received kidney grafts, followed by a second TBI and recipient leukocyte infusion, rejected their marrow graft without rejecting their transplanted kidneys for periods greater than one year. Mixed chimerism may be clinically reverted to 100% recipient without rejection of a kidney allograft. This model has potential applications in understanding the mechanism of split tolerance. This finding may have application towards minimizing the risk of GVHD in solid organ transplant patients given hematopoietic cell transplantation from HLA-identical donors.