Promotion and prevention of autoimmune disease by CD8+ T cells

Until recently, little was known about the importance of CD8+ T effectors in promoting and preventing autoimmune disease development. CD8+ T cells can oppose or promote autoimmune disease through activities as suppressor cells and as cytotoxic effectors. Studies in several distinct autoimmune models and data from patient samples are beginning to establish the importance of CD8+ T cells in these diseases and to define the mechanisms by which these cells influence autoimmunity. CD8+ effectors can promote disease via dysregulated secretion of inflammatory cytokines, skewed differentiation profiles and inappropriate apoptosis induction of target cells, and work to block disease by eliminating self-reactive cells and self-antigen sources, or as regulatory T cells. Defining the often major contribution of CD8+ T cells to autoimmune disease and identifying the mechanisms by which they alter the pathogenesis of disease is a rapidly expanding area of study and will add valuable information to our understanding of the kinetics, pathology and biology of autoimmune disease.     

Metabolic responses of clam Ruditapes philippinarum exposed to its pathogen Vibrio tapetis in relation to diet

We investigated the effect of brown ring disease (BRD) development and algal diet on energy reserves and activity of enzymes related to energy metabolism, antioxidant system and immunity in Manila clam, Ruditapes philippinarum. We found that algal diet did not impact the metabolic response of clams exposed to Vibrio tapetis. At two days post-injection (dpi), activities of superoxide dismutase and glutathione peroxidase (GPx) decreased whereas activities of nitric oxide synthase (iNOS) and catalase increased in infected clams, although no clinical signs were visible (BRD−). At 7 dpi, activities of several antioxidant and immune-related enzymes were markedly increased in BRD-likely indicating an efficient reactive oxygen species (ROS) scavenging compared to animals which developed clinical signs of BRD (BRD+). Therefore, resistance to BRD clinical signs appearance was associated with higher detoxification of ROS and enhancement of immune response. This study provides new biochemical indicators of disease resistance and a more comprehensive view of the global antioxidant response of clam to BRD development.     

Ingestion of oats and barley in patients with celiac disease mobilizes cross-reactive T cells activated by avenin peptides and immuno-dominant hordein peptides

Celiac disease (CD) is a common CD4⁺ T cell mediated enteropathy driven by gluten in wheat, rye, and barley. Whilst clinical feeding studies generally support the safety of oats ingestion in CD, the avenin protein from oats can stimulate intestinal gluten-reactive T cells isolated from some CD patients in vitro. Our objective was to establish whether ingestion of oats or other grains toxic in CD stimulate an avenin-specific T cell response in vivo.We fed participants a meal of oats (100 g/day over 3 days) to measure the in vivo polyclonal avenin-specific T cell responses to peptides contained within comprehensive avenin peptide libraries in 73 HLA-DQ2.5⁺ CD patients. Grain cross-reactivity was investigated using oral challenge with wheat, barley, and rye.Avenin-specific responses were observed in 6/73 HLA-DQ2.5⁺ CD patients (8%), against four closely related peptides. Oral barley challenge efficiently induced cross-reactive avenin/hordein-specific T cells in most CD patients, whereas wheat or rye challenge did not. In vitro, immunogenic avenin peptides were susceptible to digestive endopeptidases and showed weak HLA-DQ2.5 binding stability.Our findings indicate that CD patients possess T cells capable of responding to immuno-dominant hordein epitopes and homologous avenin peptides ex vivo, but the frequency and consistency of these T cells in blood is substantially higher after oral challenge with barley compared to oats. The low rates of T cell activation after a substantial oats challenge (100 g/d) suggests that doses of oats commonly consumed are insufficient to cause clinical relapse, and supports the safety of oats demonstrated in long-term feeding studies.     

Early pathogenesis during infectious bursal disease in susceptible chickens is associated with changes in B cell genomic methylation and loss of genome integrity

We propose a model by which an increase in the genomic modification, 5-hydroxymethylcytosine (5hmC), contributes to B cell death within the chicken bursa of Fabricus (BF) infected with infectious bursal disease virus (IBDV). Our findings indicate that, following an IBDV infection, Rhode Island Red (RIR) chickens have fewer surviving B cells and higher levels of 5hmC in the BF than the more resistant 15l line of birds. Elevated genomic 5hmC levels within the RIR BF are associated with markers of immune responses: infiltrating T cells and increased expression of CD40L, FasL and iNOS. Such changes correlate with genomic fragmentation and the presence of IBDV capsid protein, VP2. To explore the effects of CD40L, the immature B cell line, DT40, was exposed to recombinant chicken CD40L that resulted in changes in nuclear 5hmC distribution. Collectively, our observations suggest that T cell infiltration exacerbates early immunopathology within the BF during an IBDV infection contributing to B cell genomic instability and death to facilitate viral egress and immunosuppression.     

Macrophages from disease resistant B2 haplotype chickens activate T lymphocytes more effectively than macrophages from disease susceptible B19 birds

Resistance to respiratory pathogens, including coronavirus-induced infection and clinical illness in chickens has been correlated with the B (MHC) complex and differential ex vivo macrophage responses. In the current study, in vitro T lymphocyte activation measured by IFNγ release was significantly higher in B2 versus B19 haplotypes. AIV infection of macrophages was required to activate T lymphocytes and prior in vivo exposure of chickens to NP AIV plasmid enhanced responses to infected macrophages. This study suggests that the demonstrated T lymphocyte activation is in part due to antigen presentation by the macrophages as well as cytokine release by the infected macrophages, with B2 haplotypes showing stronger activation. These responses were present both in CD4 and CD8 T lymphocytes. In contrast, T lymphocytes stimulated by ConA showed greater IFNγ release of B19 haplotype cells, further indicating the greater responses in B2 haplotypes to infection is due to macrophages, but not T cells. In summary, resistance of B2 haplotype chickens appears to be directly linked to a more vigorous innate immune response and the role macrophages play in activating adaptive immunity.     

Beta-cell specific production of IL6 in conjunction with a mainly intracellular but not mainly surface viral protein causes diabetes

Inflammatory mechanisms play a key role in the pathogenesis of type 1 and type 2 diabetes. IL6, a pleiotropic cytokine with impact on immune and non-immune cell types, has been proposed to be involved in the events causing both forms of diabetes and to play a key role in experimental insulin-dependent diabetes development. The aim of this study was to investigate how beta-cell specific overexpression of IL-6 influences diabetes development. We developed two lines of rat insulin promoter (RIP)-lymphocytic choriomeningitis virus (LCMV) mice that also co-express IL6 in their beta-cells. Expression of the viral nucleoprotein (NP), which has a predominantly intracellular localization, together with IL6 led to hyperglycemia, which was associated with a loss of GLUT-2 expression in the pancreatic beta-cells and infiltration of CD11b⁺ cells, but not T cells, in the pancreas. In contrast, overexpression of the LCMV glycoprotein (GP), which can localize to the surface, with IL-6 did not lead to spontaneous diabetes, but accelerated virus-induced diabetes by increasing autoantigen-specific CD8⁺ T cell responses and reducing the regulatory T cell fraction, leading to increased pancreatic infiltration by CD4⁺ and CD8⁺ T cells as well as CD11b⁺ and CD11c⁺ cells. The production of IL-6 in beta-cells acts prodiabetic, underscoring the potential benefit of targeting IL6 in diabetes.     

Excess iodine promotes apoptosis of thyroid follicular epithelial cells by inducing autophagy suppression and is associated with Hashimoto thyroiditis disease

The incidence of the autoimmune thyroid disease Hashimoto thyroiditis (HT) has increased in recent years, and increasing evidence supports the contribution of excess iodine intake to thyroid disease. In this study, we examined the status of autophagy and apoptosis in thyroid tissues obtained from patients with HT, and we determined the effects of excessive iodine on the autophagy and apoptosis of thyroid follicular cells (TFCs) in an attempt to elucidate the effects of excess iodine on HT development. Our results showed decreases in the autophagy-related protein LC3B-II, and increases in caspase-3 were observed in thyroid tissues from HT patients. Interestingly, the suppression of autophagy activity in TFCs was induced by excess iodine in vitro, and this process is mediated through transforming growth factor-β1 downregulation and activation of the Akt/mTOR signaling pathway. In addition, excess iodine induced autophagy suppression and enhanced reactive oxygen species (ROS) production and apoptosis of TFCs, which could be rescued by the activation of autophagy. Taken together, our results demonstrated that excess iodine contributed to autophagy suppression and apoptosis of TFCs, which could be important factors predisposing to increased risk of HT development.     

Thymic CCL2 influences induction of T-cell tolerance

Thymic epithelial cells (TEC) and dendritic cells (DC) play a role in T cell development by controlling the selection of the T cell receptor repertoire. DC have been described to take up antigens in the periphery and migrate into the thymus where they mediate tolerance via deletion of autoreactive T cells, or by induction of natural regulatory T cells. Migration of DC to thymus is driven by chemokine receptors. CCL2, a major ligand for the chemokine receptor CCR2, is an inflammation-associated chemokine that induces the recruitment of immune cells in tissues. CCL2 and CCR2 are implicated in promoting experimental autoimmune encephalomyelitis (EAE), a mouse model for multiple sclerosis. We here show that CCL2 is constitutively expressed by endothelial cells and TEC in the thymus. Transgenic mice overexpressing CCL2 in the thymus showed an increased number of thymic plasmacytoid DC and pronounced impairment of T cell development. Consequently, CCL2 transgenic mice were resistant to EAE. These findings demonstrate that expression of CCL2 in thymus regulates DC homeostasis and controls development of autoreactive T cells, thus preventing development of autoimmune diseases.     

The RND protein is involved in the vulnibactin export system in Vibrio vulnificus M2799

Vibrio vulnificus, an opportunistic marine bacterium that causes a serious, often fatal, infection in humans, requires iron for its pathogenesis. This bacterium exports vulnibactin for iron acquisition from the environment. The mechanisms of vulnibactin biosynthesis and ferric-vulnibactin uptake systems have recently been reported, while the vulnibactin export system has not been reported. Mutant growth under low-iron concentration conditions and a bioassay of the culture supernatant indicate that the VV1_0612 protein plays a crucial role in the vulnibactin secretion as a component of the resistance-nodulation-division (RND)-type efflux system in V. vulnificus M2799. To identify which RND protein(s) together with VV1_0612 TolC constituted the RND efflux system for vulnibactin secretion, deletion mutants of 11 RND protein-encoding genes were constructed. The growth inhibition of a multiple mutant (Δ11) of the RND protein-encoding genes was observed 6 h after the beginning of the culture. Furthermore, ΔVV1_1681 exhibited a growth curve that was similar to that of Δ11, while the multiple mutant except ΔVV1_1681 showed the same growth as the wild-type strain. These results indicate that the VV1_1681 protein is involved in the vulnibactin export system of V. vulnificus M2799. This is the first genetic evidence that vulnibactin is secreted through the RND-type efflux systems in V. vulnificus.