One of the major problems with organ transplantation is preventing the recipient’s immune system from rejecting the new organ. Currently, patients must follow a strict regime of immunosuppressive drugs for their entire life, which can seriously compromise their immune system and place them at significant risk. The development of a method to induce long-term drug-free acceptance of transplanted tissue and/or organs would have tremendous implications for both patients and the health care system. Research on a newly discovered class of cells called T regulatory cells (Tregs) is focused on finding a better solution to the problem of organ rejection. While researchers know that Tregs are capable of suppressing the activity of other T cells and that they play a significant role in regulating immune response, they do not have a clear understanding of the molecular mechanisms which trigger these actions. Natasha Crellin is studying the characteristics and molecular markers unique to Tregs, aiming to provide further understanding of the differentiation and function of these cells. The goal of her research is to better understand the potential for manipulating the body’s own immune response to replace use of immunosuppressive drugs in preventing organ rejection following transplantation.