The cross-priming capacity and direct presentation potential of an autoantigen are separable and inversely related properties

We investigated whether a prevalent epitope of the β-cell-specific autoantigen islet-specific glucose-6-phosphatase catalytic subunit-related protein (IGRP206-214) reaches regional Ag-presentation pathways via unprocessed polypeptide chains, as free IGRP206-214 peptide or via preformed IGRP206-214/K(d) complexes. This was accomplished by expressing bacterial artificial chromosome transgenes encoding wild-type (stable) or ubiquitinated (unstable) forms of IGRP in IGRP-deficient NOD mice carrying MHC class I-deficient β-cells, dendritic cells, or B cells. We investigated the ability of the pancreatic lymph nodes of these mice to prime naive IGRP206-214-reactive CD8(+) T cells in vivo, either in response to spontaneous Ag shedding, or to synchronized forms of β-cell necrosis or apoptosis. When IGRP was made unstable by targeting it for proteasomal degradation within β-cells, the cross-priming, autoimmune-initiating potential of this autoantigen (designated autoantigenicity) was impaired. Yet at the same time, the direct presentation, CTL-targeting potential of IGRP (designated pathogenicity) was enhanced. The appearance of IGRP206-214 in regional Ag-presentation pathways was dissociated from transfer of IGRP206-214 or IGRP206-214/K(d) from β cells to dendritic cells. These results indicate that autoantigenicity and pathogenicity are separable and inversely related properties and suggest that pathogenic autoantigens, capable of efficiently priming CTLs while marking target cells for CTL-induced killing, may have a critical balance of these two properties.

Pharmacological inhibition of NOX reduces atherosclerotic lesions, vascular ROS and immune-inflammatory responses in diabetic Apoe(-/-) mice

AIMS/HYPOTHESIS

Enhanced vascular inflammation, immune cell infiltration and elevated production of reactive oxygen species (ROS) contribute significantly to pro-atherogenic responses in diabetes. We assessed the immunomodulatory role of NADPH oxidase (NOX)-derived ROS in diabetes-accelerated atherosclerosis.

METHODS

Diabetes was induced in male Apoe(-/-) mice with five daily doses of streptozotocin (55 mg kg(-1) day(-1)). Atherosclerotic plaque size, markers of ROS and immune cell accumulation were assessed in addition to flow cytometric analyses of cells isolated from the adjacent mediastinal lymph nodes (meLNs). The role of NOX-derived ROS was investigated using the NOX inhibitor, GKT137831 (60 mg/kg per day; gavage) administered to diabetic and non-diabetic Apoe(-/-) mice for 10 weeks.

RESULTS

Diabetes increased atherosclerotic plaque development in the aortic sinus and this correlated with increased lesional accumulation of T cells and CD11c(+) cells and altered T cell activation in the adjacent meLNs. Diabetic Apoe(-/-) mice demonstrated an elevation in vascular ROS production and expression of the proinflammatory markers monocyte chemoattractant protein 1, vascular adhesion molecule 1 and IFNγ. Blockade of NOX-derived ROS using GKT137831 prevented the diabetes-mediated increase in atherosclerotic plaque area and associated vascular T cell infiltration and also significantly reduced vascular ROS as well as markers of inflammation and plaque necrotic core area.

CONCLUSIONS/INTERPRETATION

Diabetes promotes pro-inflammatory immune responses in the aortic sinus and its associated lymphoid tissue. These changes are associated with increased ROS production by NOX. Blockade of NOX-derived ROS using the NOX inhibitor GKT137831 is associated with attenuation of these changes in the immune response and reduces the diabetes-accelerated development of atherosclerotic plaques in Apoe(-/-) mice.

Baculoviral inhibitors of apoptosis repeat containing (BIRC) proteins fine-tune TNF-induced nuclear factor κB and c-Jun N-terminal kinase signalling in mouse pancreatic beta cells

AIMS/HYPOTHESIS

For beta cells, contact with TNF-α triggers signalling cascades that converge on pathways important for cell survival and inflammation, specifically nuclear factor κB (NF-κB), c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase pathways. Here, we investigated the function of baculoviral inhibitors of apoptosis repeat containing (BIRC) proteins in regulating TNF signalling cascades.

METHODS

TNF regulation of Birc genes was studied by mRNA expression and promoter analysis. Birc gene control of cell signalling was studied in beta cell lines, and in islets from Birc2(-/-) and Birc3(-/-) mice, and from Birc3(-/-) Birc2Δ beta cell mice that selectively lack Birc2 and Birc3 (double knockout [DKO]). Islet function was tested by intraperitoneal glucose tolerance test and transplantation.

RESULTS

TNF-α selectively induced Birc3 in beta cells, which in turn was sufficient to drive and potentiate NF-κB reporter activity. Conversely, Birc3(-/-) islets exhibited delayed TNF-α-induced IκBα degradation with reduced expression of Ccl2 and Cxcl10. DKO islets showed a further delay in IκBα degradation kinetics. Surprisingly, DKO islets exhibited stimulus-independent and TNF-dependent hyperexpression of TNF target genes A20 (also known as Tnfaip3), Icam1, Ccl2 and Cxcl10. DKO islets showed hyperphosphorylation of the JNK-substrate, c-Jun, while a JNK-antagonist prevented increases of Icam1, Ccl2 and Cxcl10 expression. Proteosome blockade of MIN6 cells phenocopied DKO islets. DKO islets showed more rapid loss of glucose homeostasis when challenged with the inflammatory insult of transplantation.

CONCLUSIONS/INTERPRETATION

BIRC3 provides a feed-forward loop, which, with BIRC2, is required to moderate the normal speed of NF-κB activation. Paradoxically, BIRC2 and BIRC3 act as a molecular brake to rein in activation of the JNK signalling pathway. Thus BIRC2 and BIRC3 fine-tune NF-κB and JNK signalling to ensure transcriptional responses are appropriately matched to extracellular inputs. This control is critical for the beta cell's stress response.

Advanced glycation end products as environmental risk factors for the development of type 1 diabetes

The globally rising incidence of Type 1 diabetes (T1D) is no longer restricted to individuals with higher risk genotypes, but is now significantly increasing in a population with lower risk genotypes, likely as the result of environmental factors. In this review, we discuss the potential of advanced glycation end products (AGEs) as environmental contributors to the development of T1D. AGEs are nonenzymatically formed protein modifications found in the body, as well as, consumed in our daily diets. To date, many studies have provided evidence of AGE involvement in β cell dysfunction, whether by AGE modification itself or via interaction with AGE receptors. The receptor for AGE (RAGE) and AGE-receptor-1 (AGE-R1) are of particular interest, given that studies have demonstrated the deleterious effects of RAGE modulation and the protection afforded by AGE-R1 in the context of diabetes. More interestingly, we have recently found that two RAGE polymorphism are predictive of T1D in humans while the third is protective. Moreover, soluble RAGE (sRAGE) levels (a circulating competitive inhibitor of RAGE) were greatly reduced at seroconversion to autoantibodies in both children on high risk of T1D background and in an animal model of autoiummune diabetes. Taken together with the fact that AGEs have also shown to be involved in immunomodulation, it is tempting to postulate that dietary AGEs, RAGE and even AGE-R1 could be working synergistically or independently to breach the tightly regulated immune system, providing a missing link in the development of T1D.

Driven dynamics and rotary echo of a qubit tunably coupled to a harmonic oscillator

We have investigated the driven dynamics of a superconducting flux qubit that is tunably coupled to a microwave resonator. We find that the qubit experiences an oscillating field mediated by off-resonant driving of the resonator, leading to strong modifications of the qubit Rabi frequency. This opens an additional noise channel, and we find that low-frequency noise in the coupling parameter causes a reduction of the coherence time during driven evolution. The noise can be mitigated with the rotary-echo pulse sequence, which, for driven systems, is analogous to the Hahn-echo sequence.

Associations between the distance traveled from sale barns to commercial feedlots in the United States and overall performance, risk of respiratory disease, and cumulative mortality in feeder cattle during 1997 to 2009

Most beef cattle are transported at least once during their lives, and this potentially stressful practice may affect subsequent health and performance. Limited research is available quantifying the effects of transport on feedlot performance and health, and particularly the risk of bovine respiratory disease complex (BRD), which is the most common disease of weaned calves after arrival to the feedlot. The objective of this retrospective study was to determine potential associations between distance traveled (DTV) during transportation with health (cumulative BRD morbidity and mortality of all causes) and performance (ADG and HCW) parameters in cattle cohorts (n = 14,601) that arrived to 21 U.S. commercial feedlots from 1997 to 2009. Multivariable mixed-effects negative binomial and linear regression models were employed to determine associations between health and performance outcomes with DTV and other cohort-level demographic variables. Cattle were transported a median of 552 km from origin to feedlot with a mean (± SEM) of 698 ± 4.4 km. The mean (±SEM) cumulative BRD morbidity was 4.9% ± 0.01% (median = 1.1%; range: 0 to 100%) whereas the mean (±SEM) cumulative mortality due to all causes was 1.3% ± 0.01% (median = 0.8%; range: 0 to 28.7%). Distance traveled was significantly associated (P < 0.05) with BRD morbidity, overall mortality, HCW and ADG, and its effects were modified by demographic characteristics (i.e., cohort region of origin, mean arrival BW, gender, and the season of the year) of the cohort. Knowledge of the distance traveled during transportation could allow a more precise prediction of cattle feedlot health and performance.

Autoreactive cytotoxic T lymphocytes acquire higher expression of cytotoxic effector markers in the islets of NOD mice after priming in pancreatic lymph nodes

Cytotoxic T lymphocytes (CTLs) that cause type 1 diabetes are activated in draining lymph nodes and become concentrated as fully active CTLs in inflamed pancreatic islets. It is unclear whether CTL function is driven by signals received in the lymph node or also in the inflamed tissue. We studied whether the development of cytotoxicity requires further activation in islets. Autoreactive CTLs found in the islets of diabetes-prone NOD mice had acquired much higher expression of the cytotoxic effector markers granzyme B, interferon γ, and CD107a than had those in the pancreatic lymph node (PLN). Increased expression seemed to result from stimulation in the islet itself. T cells held up from migrating from the PLN by administration of the sphingosine-1-phosphate agonist FTY720 did not increase expression of cytotoxic molecules in the PLN. Stimulation did not require antigen presentation or cytokine secretion by the target β cells because it was not affected by the absence of class I major histocompatibility complex expression or by the overexpression of suppressor of cytokine signaling-1. Activation of CD40-expressing cells stimulated increased CTL function and β-cell destruction, suggesting that signals derived from CD40-expressing cells promote the acquisition of cytotoxicity in the islet environment. These data provide in vivo evidence that stimulation of cytotoxic effector molecule expression occurs in inflamed islets and is independent of β cells.

Receptor for advanced glycation end-products (RAGE) provides a link between genetic susceptibility and environmental factors in type 1 diabetes

AIMS/HYPOTHESIS

This group of studies examines human genetic susceptibility conferred by the receptor for advanced glycation end-products (RAGE) in type 1 diabetes and investigates how this may interact with a western environment.

METHODS

We analysed the AGER gene, using 13 tag SNPs, in 3,624 Finnish individuals from the FinnDiane study, followed by AGER associations with a high risk HLA genotype (DR3)-DQA1*05-DQB1*02/DRB1*0401-DQB1*0302 (n = 546; HLA-DR3/DR4), matched in healthy newborn infants from the Finnish Type 1 Diabetes Prediction and Prevention (DIPP) Study (n = 373) using allelic analysis. We also studied islets and circulating RAGE in NODLt mice.

RESULTS

The rs2070600 and rs17493811 polymorphisms predicted increased risk of type 1 diabetes, whereas the rs9469089 SNP was related to decreased risk, on a high risk HLA background. Children from the DIPP study also showed a decline in circulating soluble RAGE levels, at seroconversion to positivity for type 1 diabetes-associated autoantibodies. Islet RAGE and circulating soluble RAGE levels in prediabetic NODLt mice decreased over time and were prevented by the AGE lowering therapy alagebrium chloride. Alagebrium chloride also decreased the incidence of autoimmune diabetes and restored islet RAGE levels.

CONCLUSIONS/INTERPRETATION

These studies suggest that inherited AGER gene polymorphisms may confer susceptibility to environmental insults. Declining circulating levels of soluble RAGE, before the development of overt diabetes, may also be predictive of clinical disease in children with high to medium risk HLA II backgrounds and this possibility warrants further investigation in a larger cohort.

Mechanisms of accelerated immune-mediated diabetes resulting from islet beta cell expression of a Fas ligand transgene

Nonobese diabetic (NOD) mice transgenic for Fas ligand (FasL) on islet beta cells (HIPFasL mice) exhibit an accelerated diabetes distinct from the normal autoimmune diabetes of NOD mice. This study was undertaken to define the mechanism underlying accelerated diabetes development in HIPFasL mice. It was found that diabetes in HIPFasL mice is dependent on the NOD genetic background, as HIPFasL does not cause diabetes when crossed into other mice strains and is lymphocyte dependent, as it does not develop in HIPFasL(SCID) mice. Diabetes development in NOD(SCID) recipients of diabetic HIPFasL splenocytes is slower than when using splenocytes from diabetic NOD mice. Beta cells from HIPFasL mice are more susceptible to cytokine-induced apoptosis than wild-type NOD beta cells, and this can be blocked with anti-FasL Ab. HIPFasL islets are more rapidly destroyed than wild-type islets when transplanted into nondiabetic NOD mice. This confirms that FasL(+) islets do not obtain immune privilege, and instead NOD beta cells constitutively expressing FasL are more susceptible to apoptosis induced by Fas-FasL interaction. These findings are consistent with the accelerated diabetes of young HIPFasL mice being a different disease process from the autoimmune diabetes of wild-type NOD mice. The data support a mechanism by which cytokines produced by the insulitis lesion mediate up-regulation of beta cell Fas expression, resulting in suicide or fratricide of HIPFasL beta cells that overexpress FasL.

The role of Fas ligand in beta cell destruction in autoimmune diabetes of NOD mice

Fas ligand (FasL), a type 2 membrane protein belonging to the TNF family, plays an important role in the induction of cell death. Ligation of Fas receptors by FasL results in apoptosis of the Fas-expressing cell. Autoimmune diabetes results from beta cell destruction by islet-reactive T cells, a process that involves beta cell apoptosis. This raises the question of whether the FasL-Fas pathway plays a major role in beta cell death. To address this issue it is important to know whether beta cells express Fas and/or FasL and, if so, whether induction of these molecules leads to beta cell death. In fact, both Fas and FasL have been demonstrated to be expressed by beta cells in response to cytokine stimulation, although there remains an argument in the literature as to whether beta cells truly express FasL. This is largely because FasL expression has only been demonstrable by immunohistochemistry and not by flow cytometry. Transgenic NOD mice with beta cells expressing a FasL transgene develop an accelerated form of diabetes. We show here that beta cells from FasL transgenic NOD mice are more susceptible to cytokine-induced apoptosis than wild-type beta cells, consistent with the hypothesis that if beta cells express FasL then Fas-FasL interaction on the beta cell surface is able to mediate beta cell self-death in the absence of T cells. Interventions that block the Fas-FasL pathway may be useful, therefore, in the prevention or treatment of type 1 diabetes.

Interleukin-6 is required for a protective immune response to systemic Escherichia coli infection

Interleukin-6 (IL-6) is a multipotential cytokine detected in the serum of patients or experimental animals undergoing bacterial sepsis. To date, the role of IL-6 in gram-negative sepsis models has been controversial. We have used IL-6-deficient mice to investigate the role of IL-6 during virulent Escherichia coli infection and in lipopolysaccharide (LPS)-induced mortality. In this report we describe an increased susceptibility of IL-6-deficient mice to E. coli infection in terms of mortality and accumulation of viable bacteria in tissues, indicating a protective role for IL-6 during the immune response against E. coli. In contrast, mortality rates of IL-6-deficient mice and control animals undergoing LPS-induced shock did not differ, indicating that IL-6 was inconsequential for survival in this model. Furthermore, we have shown that neutrophils were crucial for resistance to E. coli in normal mice. IL-6-deficient mice were unable to efficiently induce neutrophilia in the bloodstream immediately following challenge with E. coli, in contrast to a characteristic neutrophilia induced in control animals. Prophylactic treatment of the mutant animals with recombinant IL-6 protein reverted both the deficit of neutrophilia and the accumulation of bacteria in tissues. These data clarify the role of IL-6 as protective in virulent E. coli infection and suggest that the protective effect may be at least partially mediated through neutrophils.

Post-natal lethality and neurological and gastrointestinal defects in mice with targeted disruption of the A-Raf protein kinase gene

The Ras/Raf/MEK/MAP kinase cascade transmits signals from activated cell-surface receptors to transcription factors in the nucleus and is an essential component of metazoan intracellular signaling pathways (see, for example, [1-6]). In the mouse, the Raf protein kinase family is comprised of three homologous genes, Raf-1, A-Raf and B-Raf [5] which are ubiquitously expressed in the developing embryo [7]. We have introduced into the mouse germ line a loss-of-function mutation in the X-chromosomal A-Raf gene, by homologous recombination in embryonic stem cells. On a predominantly C57 Bl/6 genetic background, A-Raf-deficient mice displayed neurological and intestinal abnormalities and died between 7 and 21 days post-partum. When the mutated allele was maintained on a predominantly 129/OLA background, by contrast, A-Raf-deficient animals survived to adulthood, did not display obvious intestinal abnormalities, were fertile, but did have a subset of the neurological defects.

Interleukin-6-deficient mice are highly susceptible to Listeria monocytogenes infection: correlation with inefficient neutrophilia

We have produced interleukin-6 (IL-6)-deficient mice to examine, in vivo, the wide variety of biological activities attributed to this multifunctional cytokine. To investigate the role of IL-6 during infectious disease, IL-6-deficient mice were challenged with sublethal doses of Listeria monocytogenes, a facultative intracellular bacterium. While normal control animals were able to clear the infection, mutant animals exhibited a high mortality rate and showed uncontrolled replication of the bacteria in the spleen and liver at 2 and 3 days postinfection. Sections of infected tissues showed an increase in the number and severity of inflammatory foci. All aspects of this phenotype in the mutant animals were completely reverted upon administration of recombinant murine IL-6 (rIL-6). Various parameters of natural killer (NK) cell and macrophage function were unaffected in the challenge of the mutant animals. However, IL-6-deficient animals failed to mount peripheral blood neutrophilia in response to listeriosis, whereas control animals displayed a prominent neutrophilia in the blood at 24 and 48 h postinfection. Additionally, we analyzed the efficacy of rIL-6 in protecting animals devoid of lymphocytes or devoid of neutrophils during listeriosis. Administration of rIL-6 was protective to animals devoid of lymphocytes, suggesting that the rIL-6 protective effect was not mediated through lymphocytes. In contrast, control and mutant animals depleted of neutrophils were refractory to the rIL-6 protective effect. These data suggest that IL-6 is critical early during listeriosis, perhaps acting by stimulating neutrophils either directly or indirectly. Additionally, these data show a promising therapeutic potential for rIL-6 administration during opportunistic infection.

Transgenic models of T-cell self tolerance and autoimmunity

Self-tolerance is generally induced by intrathymic clonal deletion of T cells with reactivity directed to antigens synthesized within the thymus (Kappler et al. 1987, Kisielow et al. 1988). It may also be induced in peripheral T cells when these encounter antigens unique to extra-thymic tissues. Two transgenic models have been particularly useful in the study of peripheral self tolerance: in one model, a known antigen is expressed in a particular extra-thymic site; in the other, the T-cell repertoire is predominantly reactive to this antigen. We, and others, have shown that expression of class I or II MHC molecules in defined extra-thymic sites leads to a state of T-cell tolerance. To account for this, we have proposed two hypotheses which have different implications for autoimmune disease. According to one, tolerance is imposed by deletion or functional silencing of specific high-affinity cytolytic T cells; alternatively, the target cell for tolerance induction may be a regulatory IL-2-producing T-cell, rather than the effector cell itself. To distinguish between these hypotheses it is essential to examine the fate of T cells which have the potential to react to the transgene product. Since the frequency of such T cells is low and there is no dominant clonotype for H-2Kb, which is the class I molecule we used, it was necessary to create double transgenic mice by mating class I transgenic mice with transgenic mice whose T-cell pool was compared of cells reactive to H-2Kb and could be detected by an antibody directed to the TCR. Initial studies showed that such T cells did persist despite the presence of antigen to which they may be reactive. If these double transgenic mice can be shown to be tolerant, they will offer a rich source of tolerant T cells for detailed investigation of their phenotype and fate, and they will be most useful in enabling us to probe the mechanisms responsible for the induction of peripheral self tolerance. Transgenic mouse technology has also been used successfully to unravel the genetic influences which may lead to or prevent autoimmunity. In particular, we have prevented autoimmune diabetes in the nonobese diabetic mouse by introducing a non-NOD MHC class II gene and further work is implicating the failure of intrathymic positive selection of a protective cell as one step in the pathogenesis of diabetes in NOD mice.