Craig Meagher

Differential Expression of CC Chemokines and the CCR5 Receptor in the Pancreas Is Associated with Progression to Type I Diabetes

We investigated the biological role of CC chemokines in the Th1-mediated pathogenesis of spontaneous type I diabetes in nonobese diabetic (NOD) mice. Whereas an elevated ratio of macrophage inflammatory protein-1α (MIP-1α):MIP-1β in the pancreas correlated with destructive insulitis and progression to diabetes in NOD mice, a decreased intrapancreatic MIP-1α:MIP-1β ratio was observed in nonobese diabetes-resistant (NOR) mice. IL-4 treatment, which prevents diabetes in NOD mice by polarizing intraislet Th2 responses, decreased CCR5 expression in islets and potentiated a high ratio of MIP-1β and monocyte chemotactic protein-1 (MCP-1): MIP-1α in the pancreas. Furthermore, NOD.MIP-1α−/− mice exhibited reduced destructive insulitis and were protected from diabetes. Neutralization of MIP-1α with specific Abs following transfer of diabetogenic T cells delayed the onset of diabetes in NOD.Scid recipients. These studies illustrate that the temporal expression of certain CC chemokines, particularly MIP-1α, and the CCR5 chemokine receptor in the pancreas is associated with the development of insulitis and spontaneous type I diabetes.

Spontaneous development of a pancreatic exocrine disease in CD28-deficient NOD mice.

Autoimmune pancreatitis (AIP) is a heterogeneous autoimmune disease in humans characterized by a progressive lymphocytic and plasmacytic infiltrate in the exocrine pancreas. In this study, we report that regulatory T cell-deficient NOD.CD28KO mice spontaneously develop AIP that closely resembles the human disease. NOD mouse AIP was associated with severe periductal and parenchymal inflammation of the exocrine pancreas by CD4+ T cells, CD8+ T cells, and B cells. Spleen CD4+ T cells were found to be both necessary and sufficient for the development of AIP. Autoantibodies and autoreactive T cells from affected mice recognized a ∼50-kDa protein identified as pancreatic amylase. Importantly, administration of tolerogenic amylase-coupled fixed spleen cells significantly ameliorated disease severity, suggesting that this protein functions as a key autoantigen. The establishment and characterization of this spontaneous pancreatic amylase-specific AIP in regulatory T cell-deficient NOD.CD28KO mice provides an excellent model for the study of disease pathogenesis and development of new therapies for human autoimmune pancreatitis.

Deficient activation and resistance to activation-induced apoptosis of cd8+ t cells is associated with defective peripheral tolerance in nonobese diabetic mice

Activation-induced cell death (AICD) is a mechanism of homeostasis that limits the clonal expansion of autoreactive T cells and regulates central and peripheral tolerance. In nonobese diabetic (NOD) mice, defects in central and peripheral tolerance are associated with a proliferative hyporesponsiveness of thymocytes and peripheral T cells elicited upon TCR activation. We investigated whether these defects in tolerance induction and hyporesponsiveness of NOD T cells manifest in an altered susceptibility to TCR-induced AICD. TCR-activated NOD splenic CD4+ and CD8+ T cells are more resistant to AICD than control strain C57BL/6, BALB/c, and NOR T cells. NOR CD4+ but not CD8+ T cells are resistant to TCR-induced AICD. Whereas c-FLIP expression is reduced in activated T cells from control strains, it persists in activated NOD CD8+ T cells and is accompanied by diminished activity of caspase-3 and -8. IL-4 reduces this c-FLIP expression and increases caspase-3 and -8 activity in activated NOD CD8+ T cells. Moreover, IL-4 and CD28 costimulation restores the susceptibility of NOD CD8+ T cells to AICD, and this is associated with increased expression of CD25, CD95, CD95L, and TNFR2. Thus, deficient activation of CD8+ T cells and their greater resistance to TCR-induced AICD may mediate defective peripheral tolerance and the development of T1D in NOD mice.

An Autoimmune Response to Odorant Binding Protein 1a Is Associated with Dry Eye in the Aire-Deficient Mouse

Sjögren’s Syndrome (SS) is a human autoimmune disease characterized by immune-mediated destruction of the lacrimal and salivary glands. In this study, we show that the Aire-deficient mouse represents a new tool to investigate autoimmune dacryoadenitis and keratoconjunctivitis sicca, features of SS. Previous work in the Aire-deficient mouse suggested a role for α-fodrin, a ubiquitous Ag, in the disease process. Using an unbiased biochemical approach, however, we have identified a novel lacrimal gland autoantigen, odorant binding protein 1a, targeted by the autoimmune response. This novel autoantigen is expressed in the thymus in an Aire-dependent manner. The results from our study suggest that defects in central tolerance may contribute to SS and provide a new and clinically relevant model to investigate the pathogenic mechanisms in lacrimal gland autoimmunity and associated ocular surface sequelae.

CCL4 Protects From Type 1 Diabetes by Altering Islet β-Cell–Targeted Inflammatory Responses

We previously reported that interleukin (IL)-4 treatment of nonobese diabetic (NOD) mice elevates intrapancreatic CCL4 expression and protects from type 1 diabetes. Here, we show that antibody neutralization of CCL4 abrogates the ability of T-cells from IL-4–treated NOD mice to transfer protection against type 1 diabetes. Intradermal delivery of CCL4 via a plasmid vector stabilized by incorporation of the Epstein-Barr virus EBNA1/oriP episomal maintenance replicon (pHERO8100-CCL4) to NOD mice beginning at later stages of disease progression protects against type 1 diabetes. This protection was associated with a Th2-like response in the spleen and pancreas; decreased recruitment of activated CD8+ T-cells to islets, accompanied by diminished CCR5 expression on CD8+ T-cells; and regulatory T-cell activity in the draining pancreatic lymph nodes. Thus, inflammatory responses that target islet β-cells are suppressed by CCL4, which implicates the use of CCL4 therapeutically to prevent type 1 diabetes.

Neutralization of Interleukin-16 Protects Nonobese Diabetic Mice From Autoimmune Type 1 Diabetes by a CCL4-Dependent Mechanism

OBJECTIVE The progressive infiltration of pancreatic islets by lymphocytes is mandatory for development of autoimmune type 1 diabetes. This inflammatory process is mediated by several mediators that are potential therapeutic targets to arrest development of type 1 diabetes. In this study, we investigate the role of one of these mediators, interleukin-16 (IL-16), in the pathogenesis of type 1 diabetes in NOD mice. RESEARCH DESIGN AND METHODS At different stages of progression of type 1 diabetes, we characterized IL-16 in islets using GEArray technology and immunoblot analysis and also quantitated IL-16 activity in cell migration assays. IL-16 expression was localized in islets by immunofluorescence and confocal imaging. In vivo neutralization studies were performed to assess the role of IL-16 in the pathogenesis of type 1 diabetes. RESULTS The increased expression of IL-16 in islets correlated with the development of invasive insulitis. IL-16 immunoreactivity was found in islet infiltrating T-cells, B-cells, NK-cells, and dendritic cells, and within an insulitic lesion, IL-16 was derived from infiltrating cells. CD4+ and CD8+ T-cells as well as B220+ B-cells were identified as sources of secreted IL-16. Blockade of IL-16 in vivo protected against type 1 diabetes by interfering with recruitment of CD4+ T-cells to the pancreas, and this protection required the activity of the chemokine CCL4. CONCLUSIONS IL-16 production by leukocytes in islets augments the severity of insulitis during the onset of type 1 diabetes. IL-16 and CCL4 appear to function as counterregulatory proteins during disease development. Neutralization of IL-16 may represent a novel therapy for the prevention of type 1 diabetes.

NK Cells Are Not Required for Spontaneous Autoimmune Diabetes in NOD Mice

NK cells have been shown to either promote or protect from autoimmune diseases. Several studies have examined the role of receptors preferentially expressed by NK cells in the spontaneous disease of NOD mice or the direct role of NK cells in acute induced disease models of diabetes. Yet, the role of NK cells in spontaneous diabetes has not been directly addressed. Here, we used the NOD.NK1.1 congenic mouse model to examine the role of NK cells in spontaneous diabetes. Significant numbers of NK cells were only seen in the pancreas of mice with disease. Pancreatic NK cells displayed an activated surface phenotype and proliferated more than NK cells from other tissues in the diseased mice. Nonetheless, depletion of NK cells had no effect on dendritic cell maturation or T cell proliferation. In spontaneous disease, the deletion of NK cells had no significant impact on disease onset. NK cells were also not required to promote disease induced by adoptively transferred pathogenic CD4+ T cells. Thus, NK cells are not required for spontaneous autoimmune diabetes in NOD mice.

Failure in immune regulation begets IDDM in NOD mice.

The nonobese diabetic (NOD) mouse model of insulin-dependent diabetes mellitus (IDDM) has provided evidence which suggests that an important mechanism of the induction of this T-cell-mediated autoimmune disease is a failure in immune regulation. The role of T-cell immune dysregulation in the initiation of diabetes is the focus of this review. Immunological mechanisms such as T-cell anergy and deficient T-cell-mediated suppression are discussed as mediators of IDDM susceptibility. In particular, T helper (Th) 2 cell anergy may be responsible for defective regulation of autoreactive effector T-cells. Therapies designed to overcome these T-cell-mediated deficiencies may prevent IDDM onset.

Response to Comment on: Meagher et al. Neutralization of Interleukin-16 Protects Nonobese Diabetic Mice From Autoimmune Type 1 Diabetes by a CCL4-Dependent Mechanism. Diabetes 2010;59:2862–2871

We thank Vendrame and Dotta (1) for their interesting perspective regarding our recently published study investigating the role of interleukin-16 (IL-16) in the development of insulitis and type 1 diabetes in female NOD mice (2). On the basis of previous studies correlating suboptimal activation of caspase-3 with the development of autoimmunity in the clinical setting (3,4), they propose a similar condition might exist in NOD mice, resulting …