No abstract

IL-17–producing T cells are regarded as potential pathogenic T cells in the induction of autoimmune diseases. Previously, we have shown that injection of adjuvants containing Mycobacterium, such as CFA or bacillus Calmette-Guérin, can prevent type 1 diabetes in NOD mice. We injected NOD mice with mycobacterial products s.c. and analyzed the IL-17–producing cells from the draining lymph nodes and spleen by restimulating whole-cell populations or CD4+ T cells in vitro with or without IL-17–polarizing cytokines. Mice receiving CFA had a concomitant rise in the level of IL-17, IL-22, IL-10, and IFN-γ in the draining lymph node and spleen. Adoptive transfer of splenocytes from CFA-injected NOD mice polarized with TGF-β plus IL-6 or IL-23 delayed the development of diabetes in recipient mice. IL-17–producing cells induced by CFA maintained their IL-17–producing ability in the recipient mice. Injection of CFA also changed the cytokine profile of cells in pancreatic tissue by increasing IL-17, IL-10, and IFN-γ cytokine gene expression. We suggest that the rise in the level of IL-17 after adjuvant therapy in NOD mice has a protective effect on type 1 diabetes development.

Mechanistic and therapeutic insights in autoimmune diabetes would benefit from a more complete identification of relevant autoantigens. BDC2.5 TCR transgenic NOD mice express transgenes for TCR Vα1 and Vβ4 chains from the highly diabetogenic BDC2.5 CD4+ T cell clone, which recognizes pancreatic β cell membrane Ags presented by NOD I-Ag7 MHC class II molecules. The antigenic epitope of BDC2.5 TCR is absent in β cells that do not express chromogranin A (ChgA) protein. However, characterization of the BDC2.5 epitope in ChgA has given inconclusive results. We have now identified a ChgA29–42 peptide within vasostatin-1, an N-terminal natural derivative of ChgA as the BDC2.5 TCR epitope. Having the necessary motif for binding to I-Ag7, it activates BDC2.5 T cells and induces an IFN-γ response. More importantly, adoptive transfer of naive BDC2.5 splenocytes activated with ChgA29–42 peptide transferred diabetes into NOD/SCID mice.

BackgroundIn Type 1 diabetes, the insulin-producing β-cells within the pancreatic islets of Langerhans are destroyed. We showed previously that immunotherapy with Bacillus Calmette-Guerin (BCG) or complete Freund’s adjuvant (CFA) of non-obese diabetic (NOD) mice can prevent disease process and pancreatic β-cell loss. This was associated with increased islet Regenerating (Reg) genes expression, and elevated IL-22-producing Th17 T-cells in the pancreas.ResultsWe hypothesized that IL-22 was responsible for the increased Reg gene expression in the pancreas. We therefore quantified the Reg1, Reg2, and Reg3δ (INGAP) mRNA expression in isolated pre-diabetic NOD islets treated with IL-22. We measured IL-22, and IL-22 receptor(R)-α mRNA expression in the pancreas and spleen of pre-diabetic and diabetic NOD mice. Our results showed: 1) Reg1 and Reg2 mRNA abundance to be significantly increased in IL-22-treated islets in vitro; 2) IL-22 mRNA expression in the pre-diabetic mouse pancreas increased with time following CFA treatment; 3) a reduced expression of IL-22Rα following CFA treatment; 4) a down-regulation in Reg1 and Reg2 mRNA expression in the pancreas of pre-diabetic mice injected with an IL-22 neutralizing antibody; and 5) an increased islet β-cell DNA synthesis in vitro in the presence of IL-22.ConclusionsWe conclude that IL-22 may contribute to the regeneration of β-cells by up-regulating Regenerating Reg1 and Reg2 genes in the islets.

1 S. M. B. and E. N. contributed equally to this work. SummaryT helper type 17 (Th17) cells have been shown to be pathogenic in autoimmune diseases; however, their role in type 1 diabetes (T1D) remains inconclusive. We have found that Th17 differentiation of CD4 1 T cells from BDC2Á5 T cell receptor transgenic non-obese diabetic (NOD) mice can be driven by interleukin (IL)-23 1 IL-6 to produce large amounts of IL-22, and these cells induce T1D in young NOD mice upon adoptive transfer. Conversely, polarizing these cells with transforming growth factor (TGF)-b 1 IL-6 led to non-diabetogenic regulatory Th17 (T reg 17) cells that express high levels of aryl hydrocarbon receptor (AhR) and IL-10 but produced much reduced levels of IL-22. The diabetogenic potential of these Th17 subsets was assessed by adoptive transfer studies in young NOD mice and not NOD.severe combined immunodeficient (SCID) mice to prevent possible transdifferentiation of these cells in vivo. Based upon our results, we suggest that both pathogenic Th17 cells and non-pathogenic regulatory T reg 17 cells can be generated from CD4 1 T cells under appropriate polarization conditions. This may explain the contradictory role of Th17 cells in T1D. The IL-17 producing T reg 17 cells offer a novel regulatory T cell population for the modulation of autoimmunity.