Project Summary/Abstract Based on pre-clinical studies, a compelling rationale has emerged for clinical testing of regulatory dendritic cells (DCreg) to improve organ transplant survival. Importantly, using a robust, clinically-relevant, non-human primate model and minimal immunosuppression, we have shown that infusion of DCreg, one week before transplant, can safely prolong renal allograft survival, without evidence of host sensitization. This therapeutic effect is associated with selective attenuation of donor-specific T memory cell responses, an important barrier to promotion of long-term graft survival. We have generated GMP grade human DCreg from elutriated blood monocytes and demonstrated both their stable resistance to maturation under inflammatory conditions in vitro and their ability to negatively regulate alloreactive T cell responses. We have also established release criteria for clinical testing. Based on these accomplishments and with the support of an R34 clinical trial planning grant, we have, in conjunction with DAIT program officers, completed the clinical trial protocol. We have also finalized scale-up manufacturing SOPs for DCreg production, completed design of the mechanistic studies, obtained the requisite approval (IND) from the FDA, established the framework for clinical trial operation and management, and the statistical considerations and analytical plan. We are thus well-prepared and ready to conduct the proposed clinical trial. This is a novel and unique approach to regulatory immune cell therapy in organ transplantation. We hypothesize that donor-derived DCreg, generated ex vivo and administered prospectively to live donor renal transplant recipients treated with conventional immunosuppression, will be safe and induce immunological changes conducive to improved graft survival. Our two Specific Aims are: Aim 1: To conduct a first-in-human, open-label, single center phase 1 dose escalation safety study in adult recipients of de novo, live donor renal transplants. Patients will receive standard-of-care immunosuppression. One week before transplantation, however, they will receive a single infusion of donor-derived DCreg in combination with mycophenolic acid. While this is a safety and feasibility trial, data that we acquire during the course of the trial may enable us to conduct a preliminary examination of efficacy. Aim 2: To conduct sequential immunological analyses of the DCreg recipients. We will perform detailed mechanistic studies critical to understanding the outcome of the study and potential effects of the infused cells on the alloimmune response.