Stacey M. Bellemore

IL-22, cell regeneration and autoimmunity

IL-22 as a cytokine is described with opposing pro-inflammatory and anti-inflammatory functions. Cell regeneration, tissue remodelling and balance between commensal bacteria in the gut and host immune system are considered as anti-inflammatory features of IL-22, whereas production of IL-22 from Th17 cells links this cytokine to pro-inflammatory pathways. Th17 cells and group 3 innate lymphoid cells (ILC3) are two major producers of IL-22 and both cell types express ROR-γt and Aryl hydrocarbon receptor (AhR) transcription factors. Typically, the immune system cells are the main producers of IL-22. However, targets of this cytokine are mostly non-hematopoietic cells such as hepatocytes, keratinocytes, and epithelial cells of lung and intestine. Association of IL-22 with other cytokines or transcription factors in different cell types might explain its contrasting role in health and disease. In this review we discuss the regulation of IL-22 production by AhR- and IL-23-driven pathways. A clear understanding of the biology of IL-22 will provide new opportunities for its application to improve human health involving many debilitating conditions.

The involvement of interleukin-22 in the expression of pancreatic beta cell regenerative Reg genes

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 Reg 3δ (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-22R α following CFA treatment; 4) a down-regulation in Reg1 and Reg 2 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.

Preventative role of interleukin-17 producing regulatory T helper type 17 (Treg 17) cells in type 1 diabetes in non-obese diabetic mice.

T 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+ T cells from BDC2·5 T cell receptor transgenic non‐obese diabetic (NOD) mice can be driven by interleukin (IL)‐23 + 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)‐β + IL‐6 led to non‐diabetogenic regulatory Th17 (Treg17) 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 Treg17 cells can be generated from CD4+ T cells under appropriate polarization conditions. This may explain the contradictory role of Th17 cells in T1D. The IL‐17 producing Treg17 cells offer a novel regulatory T cell population for the modulation of autoimmunity.

Preventative role of IL‐17 producing regulatory Th17 (Treg17) cells in type 1 diabetes in NOD mice

T 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+ T cells from BDC2·5 T cell receptor transgenic non‐obese diabetic (NOD) mice can be driven by interleukin (IL)‐23 + 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)‐β + IL‐6 led to non‐diabetogenic regulatory Th17 (Treg17) 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 Treg17 cells can be generated from CD4+ T cells under appropriate polarization conditions. This may explain the contradictory role of Th17 cells in T1D. The IL‐17 producing Treg17 cells offer a novel regulatory T cell population for the modulation of autoimmunity.

Pathogenic T helper type 17 cells contribute to type 1 diabetes independently of interleukin-22.

We have shown that pathogenic T helper type 17 (Th17) cells differentiated from naive CD4+ T cells of BDC2·5 T cell receptor transgenic non‐obese diabetic (NOD) mice by interleukin (IL)‐23 plus IL‐6 produce IL‐17, IL‐22 and induce type 1 diabetes (T1D). Neutralizing interferon (IFN)‐γ during the polarization process leads to a significant increase in IL‐22 production by these Th17 cells. We also isolated IL‐22‐producing Th17 cells from the pancreas of wild‐type diabetic NOD mice. IL‐27 also blocked IL‐22 production from diabetogenic Th17 cells. To determine the functional role of IL‐22 produced by pathogenic Th17 cells in T1D we neutralized IL‐22 in vivo by using anti‐IL‐22 monoclonal antibody. We found that blocking IL‐22 did not alter significantly adoptive transfer of disease by pathogenic Th17 cells. Therefore, IL‐22 is not required for T1D pathogenesis. The IL‐22Rα receptor for IL‐22 however, increased in the pancreas of NOD mice during disease progression and based upon our and other studies we suggest that IL‐22 may have a regenerative and protective role in the pancreatic islets.

Pathogenic Th17 cells contribute to type 1 diabetes independently of IL‐22

We have shown that pathogenic T helper type 17 (Th17) cells differentiated from naive CD4+ T cells of BDC2·5 T cell receptor transgenic non‐obese diabetic (NOD) mice by interleukin (IL)‐23 plus IL‐6 produce IL‐17, IL‐22 and induce type 1 diabetes (T1D). Neutralizing interferon (IFN)‐γ during the polarization process leads to a significant increase in IL‐22 production by these Th17 cells. We also isolated IL‐22‐producing Th17 cells from the pancreas of wild‐type diabetic NOD mice. IL‐27 also blocked IL‐22 production from diabetogenic Th17 cells. To determine the functional role of IL‐22 produced by pathogenic Th17 cells in T1D we neutralized IL‐22 in vivo by using anti‐IL‐22 monoclonal antibody. We found that blocking IL‐22 did not alter significantly adoptive transfer of disease by pathogenic Th17 cells. Therefore, IL‐22 is not required for T1D pathogenesis. The IL‐22Rα receptor for IL‐22 however, increased in the pancreas of NOD mice during disease progression and based upon our and other studies we suggest that IL‐22 may have a regenerative and protective role in the pancreatic islets.

Vasostatin‐1 antigenic epitope mapping for induction of cellular and humoral immune responses to chromogranin A autoantigen in NOD mice

The chromogranin A (ChgA) 29–42 sequence is the antigenic epitope for the BDC2.5 CD4+ T‐cell receptor in NOD mice (H‐2g7). We have now characterized the binding register of the ChgA 29–42 peptide for the I‐Ag7 molecule. Truncation of the peptide demonstrated that the KCVLEVISD sequence 34–42 is the binding register and extension of this sequence by flanking residues increased its binding affinity and antigenic capacity. We employed anti‐ChgA peptide antibodies generated against different fragments of ChgA for immunostaining of pancreatic islet sections from NOD mice. A strong immuno‐staining pattern was observed for the ChgA 17–38 peptide antibodies that overlap with the ChgA 29–42 sequence. Moreover, sera from diabetic NOD mice showed elevated titers of autoantibodies to the ChgA 29–42 peptide. These findings indicate that peptides from the N‐terminal region of ChgA are able to induce cellular and humoral immune responses in NOD mice.

Anti-atherogenic peptide Ep1.B derived from apolipoprotein E induces tolerogenic plasmacytoid dendritic cells.

Tolerogenic dendritic cells (DCs) play a critical role in the induction of regulatory T cells (Tregs), which in turn suppress effector T cell responses. We have previously shown the induction of DCs from human and mouse monocytic cell lines, mouse splenocytes and human peripheral blood monocytes by a novel apolipoprotein E (ApoE)‐derived self‐peptide termed Ep1.B. We also showed that this C‐terminal region 239–252 peptide of ApoE has strong anti‐atherogenic activity and reduces neointimal hyperplasia after vascular surgery in rats and wild‐type as well as ApoE‐deficient mice. In this study, we explored the phenotype of DC subset induced by Ep1.B from monocytic cell lines and from the bone marrow‐derived cells. We found Ep1.B treatment induced cells that showed characteristics of plasmacytoid dendritic cells (pDC). We explored in‐vitro and in‐vivo effects of Ep1.B‐induced DCs on antigen‐specific T cell responses. Upon in‐vivo injection of these cells with antigen, the subsequent ex‐vivo antigen‐specific proliferation of lymph node cells and splenocytes from recipient mice was greatly reduced. Our results suggest that Ep1.B‐induced pDCs promote the generation of Treg cells, and these cells contribute to the induction of peripheral tolerance in adaptive immunity and potentially contribute its anti‐atherogenic activity.