Tolerance induction in HLA disparate living donor kidney transplantation by facilitating cell-enriched donor stem cell Infusion: The importance of durable chimerism.

Successful solid organ transplantation currently requires the life-long use of medications to suppress the immune system in order to prevent transplant rejection. Drug-based immunosuppression significantly increases the risk of infection and cancer, as well as being very costly. Development of new therapies to minimize or eliminate entirely the need for anti-rejection drugs is of great interest to the transplant community. Therapeutic cell transfer for the control of the human immune system represents a compelling approach to reduce or eliminate the need for anti-rejection drugs. Establishment of durable hematopoietic chimerism through hematopoietic stem cell transplantation (HSCT) has been shown in preclinical models and patients to lead to donor specific tolerance. However, the application HSCT is limited by the potential toxicity of conditioning regimens, the risk of graft versus host disease (GVHD) and the challenge of HLA mismatching. In this review we describe the clinical outcomes and science behind a CD8+/TCR- facilitating cell-based hematopoietic stem cell transplant approach (termed FCRx) to induce tolerance to mismatched renal allografts while minimizing the risk of graft-versus-host GVHD and achieving avoidance of long-term immunosuppressant drugs in living donor kidney transplant recipients.