s Stem Cells in Kidney Transplantation: A Review of Chimerism-Based Protocols to Induce Transplantation Tolerance

Induction of donor-specific immunological tolerance in order to eliminate the lifelong systemic immunosuppressive therapy and their deleterious side effects as well as to prevent graft loss due to acute or chronic rejection or drug toxicity has been considered the "Holy Grail" of transplantation. The only effective approach of inducing tolerance is combined organ (e.g. kidney) and donor bone marrow transplantation. The hallmark of this protocol is establishment of chimerism and preferentially mixed chimerism using non-meyloablative condition which reduces the risk of GVHD, as well as its feasibility and safety for tolerance induction even in HLA-mismatched kidney graft recipients. The focus of this review is to discuss the last findings of clinical trials mainly from three medical centers as pioneers for designing and implementing tolerance protocols using chimerism-based approaches. Finally, the merits and drawbacks of these protocols are discussed with regard to the feasibility of such protocols for deceased donor grafts and more widespread application in clinical transplantation.