The laboratory of Richard N. Pierson, III, MD, in the Center for Transplantation Sciences (CTS) at Massachusetts General Hospital explores clinically important questions in transplantation. Working primarily in a cynomolgus monkey heterotopic heart allograft model, we study the pathogenesis of chronic rejection, as well as investigate costimulation and chemokine pathway modulation as approaches to induce operational tolerance. Barriers to successful application of pig-to-human xenotransplantation are studied in lung, liver, heart, kidney and thymosternal composite tissue models, focusing on coagulation pathway regulation, costimulation pathway blockade and cell adhesion mechanisms. Extensive international collaborative interactions support these translational research projects. During the course of over 30 years working in a variety of allo and xeno models, Dr. Pierson has mentored a wide variety of pre- and postdoctoral trainees. Our research fellows benefit from our diverse array of basic and translational research projects by undertaking individual projects designed around each trainee’s scientific interests to meet their educational and career goals.