Regulatory T-cell therapy for transplantation: Howmany cells dowe need?CurrOpinOrgan Transplant 17

Regulatory T cells (Tregs) are essential to transplantation tolerance and their therapeutic efficacy is well documented in animal models. Moreover, human Tregs can be identified, isolated, and expanded in short-term ex vivo cultures so that a therapeutic product can be manufactured at relevant doses. Treg therapy is being planned at multiple transplant centers around theworld. In this article, we review topics critical to effective implementation of Treg therapy in transplantation. We will address issues such as Treg dose, antigen specificity, and adjunct therapies required for transplant tolerance induction. We will summarize technical advances in Treg manufacturing and provide guidelines for identity and purity assurance of Treg products. Clinical trial designs and Treg manufacturing plans that incorporate the most up-to-date scientific understanding in Treg biology will be essential for harnessing the tol-erogenic potential of Treg therapy in transplantation. One of themajorchallenges facing thefieldoftransplantation is the management of im-munosuppression. Although immunosuppres-sion is necessary to prevent immune attacks of the transplanted organ, it also imposes substan