The clinical practicality of treating type 1 diabetics with islet transplants obviating the need for exogenous insulin replacement became evident once the first seven successful transplants were officially announced by the Edmonton group. This study proved two major points: the technical feasibility of improved islet isolation procedures and transplantation modalities and second, that more than one allogeneic donor is required to obtain an appropriate -cell mass to treat one recipient. Apparently, necrotic and apoptotic processes during the isolation procedure dramatically reduce the number of functional -cell mass obtainable. Even with an appropriate -cell mass, islet transplants are still susceptible to autoimmune and alloimmune rejection. To protect the graft against the negative consequences of these processes, the Edmonton team used a cocktail of potent immunosuppressive drugs. The recipients are required to maintain this regimen of immunosuppression for their entire lifetime. However, this therapy does pose toxicity risks in that prolonged use of this cocktail can impair kidney and liver function. This concern is a major factor that impedes the introduction of this regimen for routine clinical use to prevent immune rejection of islet transplants in young diabetics. In contrast, tolerance induction strategies, rather than immunosuppression, appear to be the favorable approach to treat children with diabetes. In an attempt to study different tolerogenic protocols, it will become extremely important to be able to follow in vivo the activities of activated T cells simultaneously with the damage inflicted to the transplanted islets. The imaging system we are proposing herein will certainly be valuable to more quickly acquire the knowledge needed to progress from intervening in rodents to rational human trials. These methods should allow non-invasive live cell imaging in live animals. We propose the development of an optical fluorescence and luminescence-based system where the fluorescent and luminescent markers are detectable above physiologic self-fluorescent backgrounds, yet sufficiently discriminative (e.g., green versus red) to allow the monitoring of different cell types simultaneously. These constitute the main goals of this application and the basis upon which the feasibility of our tolerogenic approaches will be carefully evaluated.