James F. Markmann MD, PhD is the Chief of the Division of Transplant Surgery and Director of Clinical Operations at the Transplant Center at Massachusetts General Hospital, and the Claude Welch Professor of Surgery at Harvard Medical School. He specializes in liver, kidney, pancreas and islet transplantation as well as hemodialysis access surgery. He is active in numerous societies, editorial boards and organizations and is currently secretary of the International Pancreas and Islet Transplant Association and Councilor of the American Society of Transplant Surgeons. Dr. Markmann has published more than 300 scientific papers over the last 30 years, most in the area of immune tolerance and pancreas and islet transplantation and has held continuous NIH R01 funding for >15 years. His current research interests include: 1) understanding the mechanism of action and therapeutic potential of regulatory B cells, 2) exploring the potential of ex vivo liver perfusion to improve marginal organ function, and 3) clinical trials in transplantation tolerance and pancreatic islet transplantation. The Markmann Laboratory in the Center for Transplantation Sciences (CTS) at Massachusetts General Hospital examines the hypothesis that a small subset of B cells plays a beneficial or regulatory role in transplant tolerance within the elderly population. The research program is focused on approaches to allow beta cell replacement by transplantation in Type I diabetes. This focus has spawned three general areas of study in my laboratory: The elderly are the fastest growing segment of the population, and soon the number of people older than 65 will outnumber the number of children under five. Our group is interested in the effect of age on transplant tolerance. Data suggest that with age comes a significant resistance to transplant tolerance, and we hypothesize that hormones play a role in this resistance. Our group is interested modulating the endocrine system to reverse this barrier to tolerance.