 While significant progress has been made in the islet transplantation field, many obstacles remain that currently preclude its widespread application.Two of the most important limitations are the currently inadequate means for preventing islet rejection, and the limited supply of islets for transplantation.Current immunosuppressive regimens are capable of preventing islet failure for months to years, but the agents used in these treatments are expensive and may increase the risk for specific malignancies and opportunistic infections.