Autoimmunity is reaching epidemic proportions with tens of millions of people suffering from diseases such as multiple sclerosis, rheumatoid arthritis, type 1 diabetes (T1D), systemic lupus erythematosus and others. In addition to its financial costs, the long term complications of these diseases can be devastating. A curative therapy is desperately needed. At present, efforts to prevent or reverse autoimmune diseases have been limited by the lack of safe and effective immunotherapies. With this challenge in mind, we believe the induction of immunological tolerance is a fundamental requirement for any effective therapy. Previous studies, including numerous published reports from our ACEs group and others, have focused on the use of regulatory T cells (Tregs) as one means of restoring tolerance in autoimmunity. This notion is based on the core principle that treatment with Tregs will lead to the induction of long-term tolerance. Most significantly, there is strong evidence that self-antigen-specific Tregs are most effective to treat a variety of autoimmune diseases. However, the identification and application of these cells have been compromised by the lack of effective isolation and expansion protocols for these low frequency cells. Thus, novel approaches are necessary to address this need. Specifically, this application proposes to develop novel approaches to generate a sufficient quantity of antigen-specific Tregs capable of restoring tolerance and averting autoimmunity. These studies will be performed as a collaborative effort between the Abbas and Bluestone labs where multiple mouse models have been established and be used to rapidly test theoretical cell manipulations. These efforts will inform and enhance the bulk research efforts in his proposal develoted to human Treg studies and the development of engenerred Tregs that can be used both to study the biology of Tregs and potentially be developed for clinical application. To address these key issues, the following specific aims are proposed. Aim 1.Develop engineered antigen-specific Tregs by introducing autoreactive T cell receptors (TCRs) and other therapeutic genes. Aim 2. Assess the mechanisms and safety of cellular therapy with engineered Tregs. Aim 3. To generate high numbers of autoreactive engineered Tregs capable of suppressing pathogenic autoreactive T cell responses.