Regulatory T cells and the quest for transplant tolerance.

Many regulatory cell types exist in the immune system; they contribute to immune tolerance and immune homeostasis via different mechanisms. Therapeutic manipulation of such cell types for the induction of transplant tolerance has attracted tremendous attention. However, studies in this area have uncovered unexpected challenges, and translation of regulatory T cells toward clinical utilities is fraught with difficulties. In this review, we provide a broad overview on recent progresses in the study of regulatory T cells, highlighting the complexities of regulatory cell types and the unanticipated challenges. We also discuss the opportunities and emerging approaches in harnessing the potency of regulatory T cells in clinical transplantation.