Strategies to achieve immune tolerance in allogeneic solid organ transplantation

Organ transplantation is an effective way to treat many end-stage diseases. In order to overcome post-transplant rejection, immunosuppressive agents have been widely used, but the long-term survival of transplanted organs still has not been achieved in the clinic. For decades, tolerance is the "holy grail" that transplant immunologists have longed for. The well-known approaches to induce immune tolerance are through adoptively transferred regulatory T cells and achieving chimeric states. In addition, there are a variety of promising potential strategies, including costimulatory blockade, regulating differentiation of immune cell subgroups, adoptive infusion of immunoregulatory cells, using apoptotic cells to induce tolerance, stem cell regenerative medicine to reconstitute tissue and organs, helminthic therapy, using exosomes carrying phagocytic antigen and phagocytic vesicles to induce tolerance, and blocking CD3 and targeted clearance of memory T cells. In this paper, we review the current developments and the potential of these strategies to achieve transplantation tolerance.