Exosomes (EXOs) are secreted, nano-sized membrane vesicles that contain potent immunostimulatory materials. We have recently demonstrated that insulinoma-released EXOs can stimulate the autoimmune responses in non-obese diabetic (NOD) mice, a spontaneous disease model for type 1 diabetes (T1D). To investigate whether primary islet cells can produce EXOs, we isolated cells from the islet of Langerhans of NOD mice and cultured them in vitro. Interestingly, cultured islets release fibroblast-like, fast-replicating cells that express mesenchymal stem cell (MSC) markers including CD105 and Sca-1. These islet MSC-like cells (iMSC) release highly immunostimulatory EXOs that could activate autoreactive B and T cells endogenously primed in NOD mice. Serum exosome levels and EXO-induced IFN-γ production were positively correlated with disease progression at the early prediabetic stage. Consistent with these observations, immunohistological analysis of pancreata showed that CD105+ cells are restricted to the peri-islet area in normal islets but penetrate into the β-cell area as lymphocyte infiltration occurs. Immunization with EXOs promoted expansion of transferred diabetogenic T cells and accelerated the effector T cell-mediated destruction of islets. Thus, EXOs could be the autoantigen carrier with potent adjuvant activities and may function as the autoimmune trigger in NOD mice.
- Received May 29, 2013.
- Accepted October 23, 2013.
- © 2013 by the American Diabetes Association.
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