Transplantation is the treatment of choice for many forms of end-stage organ failure and cancers of the immune system. Due to the difficulty in finding fully compatible donors, the patient’s immune system must be suppressed with drugs to prevent it from rejecting the transplanted tissue. While necessary, these drugs suppress all immune response, causing serious side effects including increased risk for infections, cancers, damage to kidneys, hypertension, diabetes and seizures. Dr. Megan Levings is looking for a way to protect the transplanted tissue without compromising other aspects of the normal immune response. She is studying a novel class of white blood cells, known as T regulatory (Tr) cells, which are thought to have the ability to selectively suppress immune responses. Dr. Levings is exploring the molecular and cellular biology of Tr cells to better understand how they develop and act to induce an immune response. Potentially, these cells might be the basis for a more directed approach to controlling rejection.