Thomas W. H. Kay

SOCS1 Is a Critical Inhibitor of Interferon γ Signaling and Prevents the Potentially Fatal Neonatal Actions of this Cytokine

Mice lacking suppressor of cytokine signaling-1 (SOCS1) develop a complex fatal neonatal disease. In this study, SOCS1-/- mice were shown to exhibit excessive responses typical of those induced by interferon gamma (IFNgamma), were hyperresponsive to viral infection, and yielded macrophages with an enhanced IFNgamma-dependent capacity to kill L. major parasites. The complex disease in SOCS1-/- mice was prevented by administration of anti-IFNgamma antibodies and did not occur in SOCS1-/- mice also lacking the IFNgamma gene. Although IFNgamma is essential for resistance to a variety of infections, the potential toxic action of IFNgamma, particularly in neonatal mice, appears to require regulation. Our data indicate that SOCS1 is a key modulator of IFNgamma action, allowing the protective effects of this cytokine to occur without the risk of associated pathological responses.

Improvement in Outcomes of Clinical Islet Transplantation: 1999–2010

OBJECTIVE To describe trends of primary efficacy and safety outcomes of islet transplantation in type 1 diabetes recipients with severe hypoglycemia from the Collaborative Islet Transplant Registry (CITR) from 1999 to 2010. RESEARCH DESIGN AND METHODS A total of 677 islet transplant-alone or islet-after-kidney recipients with type 1 diabetes in the CITR were analyzed for five primary efficacy outcomes and overall safety to identify any differences by early (1999–2002), mid (2003–2006), or recent (2007–2010) transplant era based on annual follow-up to 5 years. RESULTS Insulin independence at 3 years after transplant improved from 27% in the early era (1999–2002, n = 214) to 37% in the mid (2003–2006, n = 255) and to 44% in the most recent era (2007–2010, n = 208; P = 0.006 for years-by-era; P = 0.01 for era alone). C-peptide ≥0.3 ng/mL, indicative of islet graft function, was retained longer in the most recent era (P < 0.001). Reduction of HbA1c and resolution of severe hypoglycemia exhibited enduring long-term effects. Fasting blood glucose stabilization also showed improvements in the most recent era. There were also modest reductions in the occurrence of adverse events. The islet reinfusion rate was lower: 48% by 1 year in 2007–2010 vs. 60–65% in 1999–2006 (P < 0.01). Recipients that ever achieved insulin-independence experienced longer duration of islet graft function (P < 0.001). CONCLUSIONS The CITR shows improvement in primary efficacy and safety outcomes of islet transplantation in recipients who received transplants in 2007–2010 compared with those in 1999–2006, with fewer islet infusions and adverse events per recipient.

Essential role for interferon-gamma and interleukin-6 in autoimmune insulin-dependent diabetes in NOD/Wehi mice.

Experimental studies in vitro suggest that cytokines are important mediators in the pathogenesis of autoimmune insulin-dependent diabetes mellitus (IDDM). However, there is little evidence for the role of cytokines in vivo, either in humans or in the spontaneous animal models of IDDM such as the NOD mouse or BB rat. To address this question, we used the model of cyclophosphamide (CYP)-induced autoimmune diabetes in the NOD/Wehi mouse to examine for (a) the production of IFN-gamma and IL-6 from isolated islets, and (b) the effect of anti IFN-gamma or anti IL-6 monoclonal antibodies on the development of diabetes. After cyclophosphamide, the majority of these mice develop of mononuclear cell infiltrate (insulitis) which by 10-14 d is associated with beta cell destruction. IFN-gamma activity at low levels (2.7 +/- 0.3 U/ml) could be detected only in culture supernatants from islets isolated at day 7 post-cyclophosphamide. In contrast, IL-6 activity progressively increased from 457 +/- 44 U/ml at day 0 to 6,020 +/- 777 U/ml at day 10. Culture of islets with anti-CD3 monoclonal antibody resulted in a significant increase in IFN-gamma activity from 41 +/- 7 U/ml at day 0 to 812 +/- 156 U/ml at day 10. Mice given either anti-IFN-gamma or anti-IL-6 antibody had a significantly reduced (P less than 0.001) incidence of diabetes and especially with IFN-gamma, decreased severity of insulitis. We conclude that IFN-gamma and IL-6 have essential roles in the pathogenesis of pancreatic islet beta cell destruction in this model.

Demonstration of islet-autoreactive CD8 T cells in insulitic lesions from recent onset and long-term type 1 diabetes patients

In situ tetramer staining reveals the presence of islet antigen-reactive CD8+ T cells in pancreatic islets from deceased type 1 diabetes patients.

Transgenic Expression of Mouse Proinsulin II Prevents Diabetes in Nonobese Diabetic Mice

IDDM in humans and in nonobese diabetic (NOD) mice is a T-cell–dependent autoimmune disease in which the β-cells of the pancreatic islets are destroyed. Several putative β-cell autoantigens have been identified, but insulin and its precursor, proinsulin, are the only ones that are β-cell specific. (Pro)insulin may be a key autoantigen in IDDM. To address the role of proinsulin in the development of IDDM, we generated NOD mice transgenic for the mouse proinsulin II gene driven off a major histocompatibility complex (MHC) class II promoter to direct expression of the transgene to MHC class II bearing cells, including those in the thymus, with the aim of deleting proinsulin-reactive T-cells. The mononuclear cell infiltration of the islets (insulitis) is almost completely absent, and diabetes is prevented in these transgenic NOD mice. The mononuclear cell infiltration of the salivary glands (sialitis) and immune responses to ovalbumin (OVA) are not altered, indicating that the protective effect of the transgene is specific for islet pathology and not due to general immunosuppression. We conclude that autoimmunity to proinsulin plays a pivotal role in the development of IDDM.

Responses against islet antigens in NOD mice are prevented by tolerance to proinsulin but not IGRP

Type 1 diabetes (T1D) is characterized by immune responses against several autoantigens expressed in pancreatic beta cells. T cells specific for proinsulin and islet-specific glucose-6-phosphatase catalytic subunit-related protein (IGRP) can induce T1D in NOD mice. However, whether immune responses to multiple autoantigens are caused by spreading from one to another or whether they develop independently of each other is unknown. As cytotoxic T cells specific for IGRP were not detected in transgenic NOD mice tolerant to proinsulin, we determined that immune responses against proinsulin are necessary for IGRP-specific T cells to develop. On the other hand, transgenic overexpression of IGRP resulted in loss of intra-islet IGRP-specific T cells but did not protect NOD mice from insulitis or T1D, providing direct evidence that the response against IGRP is downstream of the response to proinsulin. Our results suggest that pathogenic proinsulin-specific immunity in NOD mice subsequently spreads to other antigens such as IGRP.

Suppressor of Cytokine Signaling-1 Is a Critical Regulator of Interleukin-7-Dependent CD8+ T Cell Differentiation

To determine the tissue-specific functions of SOCS-1, mice were generated in which the SOCS-1 gene could be deleted in individual tissues. A reporter gene of SOCS-1 promoter activity was also inserted. Using the reporter, high SOCS-1 expression was found at the CD4(+)CD8(+) stage in thymocyte development. To investigate the function of this expression, the SOCS-1 gene was specifically deleted throughout the thymocyte/T/NKT cell compartment. Unlike SOCS-1(-/-) mice, these mice did not develop lethal multiorgan inflammation but developed multiple lymphoid abnormalities, including enhanced differentiation of thymocytes toward CD8(+) T cells and very high percentages of peripheral CD8(+) T cells with a memory phenotype (CD44(hi)CD25(lo)CD69(lo)). These phenotypes were found to correlate with hypersensitivity to the gamma-common family of cytokines.

IL-1β Breaks Tolerance through Expansion of CD25+ Effector T Cells

IL-1 is a key proinflammatory driver of several autoimmune diseases including juvenile inflammatory arthritis, diseases with mutations in the NALP/cryopyrin complex and Crohn’s disease, and is genetically or clinically associated with many others. IL-1 is a pleiotropic proinflammatory cytokine; however the mechanisms by which increased IL-1 signaling promotes autoreactive T cell activity are not clear. Here we show that autoimmune-prone NOD and IL-1 receptor antagonist-deficient C57BL/6 mice both produce high levels of IL-1, which drives autoreactive effector cell expansion. IL-1β drives proliferation and cytokine production by CD4+CD25+FoxP3− effector/memory T cells, attenuates CD4+CD25+FoxP3+ regulatory T cell function, and allows escape of CD4+CD25− autoreactive effectors from suppression. Thus, inflammation or constitutive overexpression of IL-1β in a genetically predisposed host can promote autoreactive effector T cell expansion and function, which attenuates the ability of regulatory T cells to maintain tolerance to self.

The insulin A-chain epitope recognized by human T cells is posttranslationally modified

The autoimmune process that destroys the insulin-producing pancreatic β cells in type 1 diabetes (T1D) is targeted at insulin and its precursor, proinsulin. T cells that recognize the proximal A-chain of human insulin were identified recently in the pancreatic lymph nodes of subjects who had T1D. To investigate the specificity of proinsulin-specific T cells in T1D, we isolated human CD4+ T cell clones to proinsulin from the blood of a donor who had T1D. The clones recognized a naturally processed, HLA DR4–restricted epitope within the first 13 amino acids of the A-chain (A1–13) of human insulin. T cell recognition was dependent on the formation of a vicinal disulfide bond between adjacent cysteine residues at A6 and A7, which did not alter binding of the peptide to HLA DR4. CD4+ T cell clones that recognized this epitope were isolated from an HLA DR4+ child with autoantibodies to insulin, and therefore, at risk for T1D, but not from two healthy HLA DR4+ donors. We define for the first time a novel posttranslational modification that is required for T cell recognition of the insulin A-chain in T1D.

Beta cell apoptosis in diabetes

Apoptosis of beta cells is a feature of both type 1 and type 2 diabetes as well as loss of islets after transplantation. In type 1 diabetes, beta cells are destroyed by immunological mechanisms. In type 2 diabetes abnormal levels of metabolic factors contribute to beta cell failure and subsequent apoptosis. Loss of beta cells after islet transplantation is due to many factors including the stress associated with islet isolation, primary graft non-function and allogeneic graft rejection. Irrespective of the exact mediators, highly conserved intracellular pathways of apoptosis are triggered. This review will outline the molecular mediators of beta cell apoptosis and the intracellular pathways activated.