Thymic Development of Beta-Cell Specific Regulatory T Cells in Neonatal NOD Mice

Type 1 diabetes (T1D) is a T cell-mediated autoimmune disease that involves the destruction of insulin producing β cells found within the pancreatic islets of Langerhans. Recent attention to neonatal thymocyte development has revealed a window during which central tolerance is established in an Autoimmune Regulator (Aire) dependent manner. However, expression of Chromogranin A (ChgA) within the thymus has not been detected; therefore, tolerance to ChgA may be due in part to peripheral dendritic cells (DCs) presenting ChgA to developing thymocytes. The relative contribution of thymically and peripherally derived antigens in the generation of neonatal β cell antigen specific CD4+ regulatory T cells (Tregs) is not well understood. For example, post-translational modification (PTM) of ChgA by fusion with an insulin peptide increases epitope immunogenicity by forming neo-antigens. Pathogenic T cells that are specific for neo-antigens uniquely expressed in the pancreas may escape thymic selection. Therefore, we utilized two experimental designs to test the role of peripheral antigen exposure on neonatal development of β cell specific Tregs. Firstly, we adoptively transferred dendritic cells pulsed with ChgA peptides into BDC2.5 TCR Tg mice and WT NOD mice to study the role of migratory DCs on neonatal development of ChgA Tregs. Secondly, we targeted thymic Langerin+ dendritic cells with anti-Langerin linked to ChgA peptides. In both experimental approaches, we found a robust increase in the ratio and number of ChgA specific Tregs in the presence of the hybrid insulin/chromogranin A peptide (2.5HIP) while also observing an increase in negative selection. The expansion of thymic Tregs was observed in both adult and neonatal mice. Together our data suggests neonatal exposure to PTM peptides enhances thymic development of β cell specific Tregs and may alter T1D pathogenesis. Disclosure Y. Lin: None. T. Lee: None. M. Bettini: None. M. Bettini: None.