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.

Insulin-producing β cells can partially regenerate in adult pancreatic tissues, both in human and animal models of type 1 diabetes (T1D). Previous studies have shown that treatment with mycobacterial adjuvants such as CFA and bacillus Calmette-Guérin prevents induction and recurrence of T1D in NOD mice with partial recovery of β cell mass. In this study, we investigated factors involved in the regeneration of β cells in the pancreas of NOD mice during diabetes development and after treatment with adjuvants. The Regeneration (Reg) gene family is known to be involved in regeneration of various tissues including β cells. Reg2 expression was found to be upregulated in pancreatic islets both during diabetes development and as a result of adjuvant treatment in diabetic NOD mice and in C57BL/6 mice made diabetic by streptozotocin treatment. The upregulation of Reg2 by adjuvant treatment was independent of signaling through MyD88 and IL-6 because it was not altered in MyD88 or IL-6 knockout mice. We also observed upregulation of Reg2 in the pancreas of diabetic mice undergoing β cell regenerative therapy with exendin-4 or with islet neogenesis-associated protein. Reg2 expression following adjuvant treatment correlated with a reduction in insulitis, an increase in insulin secretion, and an increase in the number of small islets in the pancreas of diabetic NOD mice and with improved glucose tolerance tests in streptozotocin-treated diabetic C57BL/6 mice. In conclusion, adjuvant immunotherapy regulates T1D in diabetic mice and induces Reg2-mediated regeneration of β cells.

Juvenile or type 1 diabetes (T1D) involves autoimmune-mediated destruction of insulin-producing β cells in the islets of Langerhans in the pancreas. Lack of insulin prevents the absorption and metabolism of glucose throughout the body by interfering with cell signaling. Cytokines have been shown to play a key role in β cell destruction and regulation of autoimmunity in T1D. The multiple roles of cytokines in T1D pathogenesis, regulation, and regeneration of β cells presents both promise and challenge for their use in immunotherapy. We found that mycobacterial adjuvants induce various regulatory T cells in the non-obese diabetic (NOD) mouse model of T1D. Cytokines produced by these cells not only regulate innate and adaptive immunity but also prevent the development of diabetes and partially restored normoglycemia in diabetic NOD mice. We discovered that adjuvant immunotherapy upregulated Regenerating (Reg) genes in the islets and induced interleukin 22 (IL-22)-producing Th17 cells. IL-22 is known to upregulate Reg gene expression in islets and could potentially induce regeneration of β cells and prevent their apoptosis. Therefore, cytokines both induce and regulate T1D and have the potential to regenerate and preserve insulin-producing β cells in the islets.

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 Mycobacteria containing products such as Bacille Calmette-Guerin (BCG) or Complete Freund Adjuvant (CFA), can prevent type 1 diabetes (T1D) in nonobese diabetic (NOD) mice. We injected NOD mice with mycobacterial products subcutaneously and analyzed the IL-17 producing cells from the draining lymph nodes and spleen by restimulating whole cell populations 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-g in the draining lymph node and spleen. Adoptive transfer of splenocytes from CFA-injected NOD mice polarized with TGF-b 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-g cytokine gene expression. Compared to wild type mice, injection of CFA into MyD88-/- mice drastically reduced but did not abolish the level of IL-17 in the lymphoid organs and pancreas indicating that the MyD88 pathway is a major pathway through which Mycobacteria exerts its effect. We suggest that the rise in the level of IL-17 after adjuvant therapy in NOD mice has a protective effect on T1D development.