PROJECT SUMMARY/ABSTRACT (30 lines or less) The premise for the proposed research stems from precedence in other diseases, such as cancer, cardiovascular, neurodegenerative, and most relevant to the current proposal, autoimmune diseases, in which extracellular vesicles (EVs) play a role in the pathophysiology and are important biomarkers for early detection. However, in human type 1 diabetes (T1D), little is known concerning EVs in cellular communication. Our overall hypothesis is that autocrine-paracrine interactions, mediated through EVs, between the islets and islet-infiltrating immune cells in the pancreas contribute to the development and progression of T1D. Our specific aims are: 1) to assess the functional impact of islet-infiltrating T-cell derived EVs (T-EV) from T1D and autoantibody+ (Aab+) donors on islet health and on distinct immune cell populations; 2) to investigate the contribution of stressed or T1D islet-derived EVs (I-EV) on immune cell phenotype and islet health; and 3) to decipher the differential protein cargo in T-EV and I-EV from T1D and Aab+ donors. To address these aims, we have assembled a team of investigators with highly relevant expertise, techniques and unique resources of cell lines and tissue samples. From 36 human tissue donors with T1D or Aab positivity, we have >600 T cell lines grown directly from the individual islets of pancreata. We have the expertise and technical ability to isolate EV from islets (I-EV) and from islet-infiltrating T cell lines (T-EV) from T1D donors. Our preliminary data indicates I-EV and T-EV have both paracrine and autocrine effects on islet health and immune cell phenotype. Our Research Plan is to generate T-EV and I-EV from donors with T1D of distinct durations or positivity for islet autoantibodies, to evaluate their effects on islet health and immune cell function, and to determine the uniquely packaged protein cargo from these EVs whose molecular composition reflects the pathophysiologic state of the disseminating cell. These studies will yield important information concerning the communication between immune cell populations and islets via EVs in the pathogenesis of T1D, and potential biomarkers or therapeutic targets for T1D.