Current State of Immunosuppression: Past, Present, and Future

The success of solid-organ transplantation was made possible by recognizing that destruction of the graft is caused by an alloimmune-mediated process. For the past decade, immunosuppressive protocols have used a combination of drugs that significantly decreased the rate of acute organ rejection. Despite advances in surgical and medical care of recipients of solid-organ transplants, long-term graft survival and patient survival have not improved during the past 2 decades. Current immunosuppression protocols include a combination of calcineurin inhibitors, such as tacrolimus, and antiproliferative agents (most commonly mycophenolate mofetil), with or without different dosing regimens of corticosteroids. Mammalian target of rapamycin inhibitors were introduced to be used in combination with cyclosporine-based therapy, but they did not gain much acceptance because of their adverse event profile. Belatacept, a costimulatory inhibitor, is currently being studied in different regimens in an effort to replace the use of calcineurin inhibitors to induce tolerance and to improve long-term outcomes. Induction therapy is now being used in more than 90% of kidney transplants and more than 50% cases of other solid-organ transplantation such as lung, heart, and intestinal transplants. As a result of these combination immunosuppressive (IS) therapy protocols, not only the incidence but also the intensity of episodes of acute rejection have decreased markedly, and at present 1-year graft and patient survival is almost 98% for kidney transplant recipients and approximately greater than 80% for heart and lung transplants. Evolving concepts include the use of donor-derived bone marrow mesenchymal cells to induce tolerance, to minimize the use of maintenance IS agents, and to prevent the development of adverse events associated with long-term use of maintenance IS therapy.