Detection of vasostatin-1-specific CD8(+) T cells in non-obese diabetic mice that contribute to diabetes pathogenesis.

Chromogranin A (ChgA) is an antigenic target of pathogenic CD4(+) T cells in a non-obese diabetic (NOD) mouse model of type 1 diabetes (T1D). Vasostatin-1 is a naturally processed fragment of ChgA. We have now identified a novel H2-K(d) -restricted epitope of vasostatin-1, ChgA 36-44, which elicits CD8(+) T cell responses in NOD mice. By using ChgA 36-44/K(d) tetramers we have determined the frequency of vasostatin-1-specific CD8(+) T cells in pancreatic islets and draining lymph nodes of NOD mice. We also demonstrate that vasostatin-1-specific CD4(+) and CD8(+) T cells constitute a significant fraction of islet-infiltrating T cells in diabetic NOD mice. Adoptive transfer of T cells from ChgA 36-44 peptide-primed NOD mice into NOD/severe combined immunodeficiency (SCID) mice led to T1D development. These findings indicate that vasostatin-1-specific CD8(+) T cells contribute to the pathogenesis of type 1 diabetes in NOD mice.

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.

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)-ß+IL-6 led to non-diabetogenic regulatory Th17 (Treg 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 Treg 17 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 Treg 17 cells offer a novel regulatory T cell population for the modulation of autoimmunity.

Reduced interferon-α production by dendritic cells in type 1 diabetes does not impair immunity to influenza virus.

The increased risk and persistence of infections in diabetic condition is probably associated with defects in the cellular immune responses. We have previously shown a decrease in the production of interferon (IFN)-α by dendritic cells (DCs) in diabetic subjects. The basal level of IFN-α in splenic plasmacytoid DCs (pDCs) is also lower in non-obese diabetic (NOD) mice compared to prediabetic mice. The objective of this study was to analyse the ability of diabetic mice to mobilize innate and CD8(+) T cell-mediated immune response to influenza A virus (IAV) with the live influenza A/Puerto Rico/8/1934 H1N1 (PR8) strain or with its immunodominant CD8(+) T cell epitopes. We found that following immunization with IAV, the level of IFN-α in diabetic mice was increased to the level in prediabetic mice. Immunization of NOD mice with the immunodominant IAV PR8 peptide induced clonal expansion of IFN-γ-producing CD8(+) T cells similar to the response observed in prediabetic mice. Thus, diabetic and prediabetic NOD mice have a similar capacity for IFN-α and IFN-γ production by pDCs and CD8(+) T cells, respectively. Therefore, the DC-related immune defect in diabetic NOD mice does not impair their capacity to develop an effective immune response to IAV. Our results suggest that reduced IFN-α production by diabetic human and mouse DCs is not an impediment to an effective immunity to IAV in type 1 diabetic subjects vaccinated with live attenuated influenza vaccine.

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.