Bone marrow chimerism as a strategy to produce tolerance in solid organ allotransplantation.
OBJECTIVE
Clinical transplant tolerance has been most successfully achieved combining hematopoietic chimerism with kidney transplantation. This review outlines this strategy in animal models and human transplantation, and possible clinical challenges.


RESULTS
Kidney transplant tolerance has been achieved through chimerism in several centers beginning with Massachusetts General Hospital's success with mixed chimerism in human leukocyte antigen (HLA)-mismatched patients and the Stanford group with HLA-matched patients, and the more recent success of the Northwestern protocol achieving full chimerism. This has challenged the original view that stable mixed chimerism is necessary for organ graft tolerance. However, among the HLA-mismatched kidney transplant-tolerant patients, loss of mixed chimerism does not lead to renal-graft rejection, and the development of host Foxp3+ regulatory T cells has been observed. Recent animal models suggest that graft tolerance through bone marrow chimerism occurs through both clonal deletion and regulatory immune cells. Further, Tregs have been shown to improve chimerism in animal models.


CONCLUSIONS
Animal studies continue to suggest ways to improve our current clinical strategies. Advances in chimerism protocols suggest that tolerance may be clinically achievable with relative safety for HLA-mismatched kidney transplants.
aCentre for Transplantation and Renal Research, Westmead Institute for Medical Research bCentre for Kidney Research, The Children's Hospital at Westmead, University of Sydney, Westmead, NSW, Australia.
Min
M
Hu
Stephen I
SI
Alexander
Shounan
S
Yi
D000818:Animals; D001854:Bone Marrow Cells / Q000166:cytology / Q000502:physiology; D016026:Bone Marrow Transplantation; D006680:HLA Antigens; D006801:Humans; D016030:Kidney Transplantation; D018183:Transplantation Chimera; D023001:Transplantation Tolerance
D006680:HLA Antigens