Islet autoimmunity in human type 1 diabetes: initiation and progression from the perspective of the beta cell.

Type 1 diabetes results from the poorly understood process of islet autoimmunity, which ultimately leads to the loss of functional pancreatic beta cells. Mounting evidence supports the notion that the activation and evolution of islet autoimmunity in genetically susceptible people is contingent upon early life exposures affecting the islets, especially beta cells. Here, we review some of the recent advances and studies that highlight the roles of these changes as well as antigen presentation and stress response pathways in beta cells in the onset and propagation of the autoimmune process in type 1 diabetes. Future progress in this area holds promise for advancing islet- and beta cell-directed therapies that could be implemented in the early stages of the disease and could be combined with immunotherapies.

Beta cell function in the early stages of type 1 diabetes: still a long way ahead of us.

The clinical onset of type 1 diabetes (namely stage 3 type 1 diabetes [T1D]) is preceded by a relatively prolonged pre-symptomatic phase featured by islet autoimmunity [1] with (Stage 2 T1D) or without (Stage 1 T1D) dysglycaemia. While islet autoimmunity is the hallmark of the underlying autoimmune process, very little evidence is available for the metabolic changes that accompany the loss of functional beta cell mass. Indeed, a steep decline of C-peptide - a surrogate marker of beta cell function - is measurable only ~6 months before the onset of Stage 3 T1D [2]. Disease modifier drugs have, there-fore, a very limited window of intervention because we lack of effective methods to track beta cell function over time and to identify early changes of insulin secretion that precedes dysglycaemia [3, 4] and clinically symptomatic diabetes. Herein, we will revise current approaches to longitudinally track beta cell function over time before the onset of Stage 3 T1D, which might be suitable for monitoring the risk for diabetes progression as well as the effectiveness of disease modifier treatments.

T cell aging as a risk factor for autoimmunity.

Immune aging is a complex process rendering the host susceptible to cancer, infection, and insufficient tissue repair. Many autoimmune diseases preferentially occur during the second half of life, counterintuitive to the concept of excess adaptive immunity driving immune-mediated tissue damage. T cells are particularly susceptible to aging-imposed changes, as they are under extreme proliferative pressure to fulfill the demands of clonal expansion and of homeostatic T cell repopulation. T cells in older adults have a footprint of genetic and epigenetic changes, lack mitochondrial fitness, and fail to maintain proteostasis, diverging them from host protection to host injury. Here, we review recent progress in understanding how the human T-cell system ages and the evidence detailing how T cell aging contributes to autoimmune conditions. T cell aging is now recognized as a risk determinant in two prototypic autoimmune syndromes; rheumatoid arthritis and giant cell arteritis. The emerging concept adds susceptibility to autoimmune and autoinflammatory disease to the spectrum of aging-imposed adaptations and opens new opportunities for immunomodulatory therapy by restoring the functional intactness of aging T cells.

Dopaminergic stimulation leads B-cell infiltration into the central nervous system upon autoimmunity.

BACKGROUND: Recent evidence has shown dopamine as a major regulator of inflammation. Accordingly, dopaminergic regulation of immune cells plays an important role in the physiopathology of inflammatory disorders. Multiple sclerosis (MS) is an inflammatory disease involving a CD4+ T-cell-driven autoimmune response to central nervous system (CNS) derived antigens. Evidence from animal models has suggested that B cells play a fundamental role as antigen-presenting cells (APC) re-stimulating CD4+ T cells in the CNS as well as regulating T-cell response by mean of inflammatory or anti-inflammatory cytokines. Here, we addressed the role of the dopamine receptor D3 (DRD3), which displays the highest affinity for dopamine, in B cells in animal models of MS. METHODS: Mice harbouring Drd3-deficient or Drd3-sufficient B cells were generated by bone marrow transplantation into recipient mice devoid of B cells. In these mice, we compared the development of experimental autoimmune encephalomyelitis (EAE) induced by immunization with a myelin oligodendrocyte glycoprotein (MOG)-derived peptide (pMOG), a model that leads to CNS-autoimmunity irrespective of the APC-function of B cells, or by immunization with full-length human MOG protein (huMOG), a model in which antigen-specific activated B cells display a fundamental APC-function in the CNS. APC-function was assessed in vitro by pulsing B cells with huMOG-coated beads and then co-culturing with MOG-specific T cells. RESULTS: Our data show that the selective Drd3 deficiency in B cells abolishes the disease development in the huMOG-induced EAE model. Mechanistic analysis indicates that although DRD3-signalling did not affect the APC-function of B cells, DRD3 favours the CNS-tropism in a subset of pro-inflammatory B cells in the huMOG-induced EAE model, an effect that was associated with higher CXCR3 expression. Conversely, the results show that the selective Drd3 deficiency in B cells exacerbates the disease severity in the pMOG-induced EAE model. Further analysis shows that DRD3-stimulation increased the expression of the CNS-homing molecule CD49d in a B-cell subset with anti-inflammatory features, thus attenuating EAE manifestation in the pMOG-induced EAE model. CONCLUSIONS: Our findings demonstrate that DRD3 in B cells exerts a dual role in CNS-autoimmunity, favouring CNS-tropism of pro-inflammatory B cells with APC-function and promoting CNS-homing of B cells with anti-inflammatory features. Thus, these results show DRD3-signalling in B cells as a critical regulator of CNS-autoimmunity.

Risk surveillance and mitigation: autoantibodies as triggers and inhibitors of severe reactions to SARS-CoV-2 infection.

COVID-19 clinical presentation differs considerably between individuals, ranging from asymptomatic, mild/moderate and severe disease which in some cases are fatal or result in long-term effects. Identifying immune mechanisms behind severe disease development informs screening strategies to predict who are at greater risk of developing life-threatening complications. However, to date clear prognostic indicators of individual risk of severe or long COVID remain elusive. Autoantibodies recognize a range of self-antigens and upon antigen recognition and binding, important processes involved in inflammation, pathogen defence and coagulation are modified. Recent studies report a significantly higher prevalence of autoantibodies that target immunomodulatory proteins including cytokines, chemokines, complement components, and cell surface proteins in COVID-19 patients experiencing severe disease compared to those who experience mild or asymptomatic infections. Here we discuss the diverse impacts of autoantibodies on immune processes and associations with severe COVID-19 disease.

Dimethyl fumarate treatment restrains the antioxidative capacity of T cells to control autoimmunity.

Dimethyl fumarate, an approved treatment for relapsing-remitting multiple sclerosis, exerts pleiotropic effects on immune cells as well as CNS resident cells. Here, we show that dimethyl fumarate exerts a profound alteration of the metabolic profile of human CD4+ as well as CD8+ T cells and restricts their antioxidative capacities by decreasing intracellular levels of the reactive oxygen species scavenger glutathione. This causes an increase in mitochondrial reactive oxygen species levels accompanied by an enhanced mitochondrial stress response, ultimately leading to impaired mitochondrial function. Enhanced mitochondrial reactive oxygen species levels not only result in enhanced T-cell apoptosis in vitro as well as in dimethyl fumarate-treated patients, but are key for the well-known immunomodulatory effects of dimethyl fumarate both in vitro and in an animal model of multiple sclerosis, i.e. experimental autoimmune encephalomyelitis. Indeed, dimethyl fumarate immune-modulatory effects on T cells were completely abrogated by pharmacological interference of mitochondrial reactive oxygen species production. These data shed new light on dimethyl fumarate as bona fide immune-metabolic drug that targets the intracellular stress response in activated T cells, thereby restricting mitochondrial function and energetic capacity, providing novel insight into the role of oxidative stress in modulating cellular immune responses and T cell-mediated autoimmunity.

100 YEARS OF INSULIN: Pancreas pathology in type 1 diabetes: an evolving story.

We review the current knowledge of pancreas pathology in type 1 diabetes. During the last two decades, dedicated efforts toward the recovery of pancreas from deceased patients with type 1 diabetes have promoted significant advances in the characterization of the pathological changes associated with this condition. The implementation of autoantibody screening among organ donors has also allowed examining pancreas pathology in the absence of clinical disease, but in the presence of serological markers of autoimmunity. The assessment of key features of pancreas pathology across various disease stages allows driving parallels with clinical disease stages. The main pathological abnormalities observed in the pancreas with type 1 diabetes are beta-cell loss and insulitis; more recently, hyperexpression of HLA class I and class II molecules have been reproduced and validated. Additionally, there are changes affecting extracellular matrix components, evidence of viral infections, inflammation, and ER stress, which could contribute to beta-cell dysfunction and the stimulation of apoptosis and autoimmunity. The increasing appreciation that beta-cell loss can be less severe at diagnosis than previously estimated, the coexistence of beta-cell dysfunction, and the persistence of key features of pancreas pathology for years after diagnosis impact the perception of the dynamics of this chronic process. The emerging information is helping the identification of novel therapeutic targets and has implications for the design of clinical trials.

The Pathophysiological Role of Heat Shock Response in Autoimmunity: A Literature Review.

Within the last two decades, there has been increasing evidence that heat-shock proteins can have a differential influence on the immune system. They can either provoke or ameliorate immune responses. This review focuses on outlining the stimulatory as well as the inhibitory effects of heat-shock proteins 27, 40, 70, 65, 60, and 90 in experimental and clinical autoimmune settings.

Prenatal cadmium exposure does not induce greater incidence or earlier onset of autoimmunity in the offspring.

We previously demonstrated that exposure of adult mice to environmental levels of cadmium (Cd) alters immune cell development and function with increases in anti-streptococcal antibody levels, as well as decreases in splenic natural regulatory T cells (nTreg) in the adult female offspring. Based on these data, we hypothesized that prenatal Cd exposure could predispose an individual to developing autoimmunity as adults. To test this hypothesis, the effects of prenatal Cd on the development of autoimmune diabetes and arthritis were investigated. Non-obese diabetic (NOD) mice were exposed to Cd in a manner identical to our previous studies, and the onset of diabetes was assessed in the offspring. Our results showed a similar time-to-onset and severity of disease to historical data, and there were no statistical differences between Cd-exposed and control offspring. Numerous other immune parameters were measured and none of these parameters showed biologically-relevant differences between Cd-exposed and control animals. To test whether prenatal Cd-exposure affected development of autoimmune arthritis, we used SKG mice. While the levels of arthritis were similar between Cd-exposed and control offspring of both sexes, the pathology of arthritis determined by micro-computed tomography (µCT) between Cd-exposed and control animals, showed some statistically different values, especially in the female offspring. However, the differences were small and thus, the biological significance of these changes is open to speculation. Overall, based on the results from two autoimmune models, we conclude that prenatal exposure to Cd did not lead to a measurable propensity to develop autoimmune disease later in life.

Regulation of autoreactive CD4 T cells by FoxO1 signaling in CNS autoimmunity.

Myelin-specific CD4 T effector cells (Teffs), Th1 and Th17 cells, are encephalitogenic in experimental autoimmune encephalomyelitis (EAE), a well-defined murine model of multiple sclerosis (MS) and implicated in MS pathogenesis. Forkhead box O 1 (FoxO1) is a conserved effector molecule in PI3K/Akt signaling and critical in the differentiation of CD4 T cells into T helper subsets. However, it is unclear whether FoxO1 may be a target for redirecting CD4 T cell differentiation and benefit CNS autoimmunity. Using a selective FoxO1 inhibitor AS1842856, we show that inhibition of FoxO1 suppressed the differentiation and expansion of Th1 cells. The transdifferentiation of Th17 cells into encephalitogenic Th1-like cells was suppressed by FoxO1 inhibition upon reactivation of myelin-specific CD4 T cells from EAE mice. The transcriptional balance skewed from the Th1 transcription factor T-bet toward the Treg transcription factor Foxp3. Myelin-specific CD4 T cells treated with the FoxO1 inhibitor were less encephalitogenic in adoptive transfer EAE studies. Inhibition of FoxO1 in T cells from MS patients significantly suppressed the expansion of Th1 cells. Furthermore, FoxO1 inhibition with AS1842856 promoted the development of functional iTreg cells. The immune checkpoint programmed cell death protein-1 (PD-1)-induced Foxp3 expression in CD4 T cells was impaired by FoxO1 inhibition. These data illustrate an important role of FoxO1 signaling in CNS autoimmunity via regulating autoreactive Teff and Treg balance.

MERTK on mononuclear phagocytes regulates T cell antigen recognition at autoimmune and tumor sites.

Understanding mechanisms of immune regulation is key to developing immunotherapies for autoimmunity and cancer. We examined the role of mononuclear phagocytes during peripheral T cell regulation in type 1 diabetes and melanoma. MERTK expression and activity in mononuclear phagocytes in the pancreatic islets promoted islet T cell regulation, resulting in reduced sensitivity of T cell scanning for cognate antigen in prediabetic islets. MERTK-dependent regulation led to reduced T cell activation and effector function at the disease site in islets and prevented rapid progression of type 1 diabetes. In human islets, MERTK-expressing cells were increased in remaining insulin-containing islets of type 1 diabetic patients, suggesting that MERTK protects islets from autoimmune destruction. MERTK also regulated T cell arrest in melanoma tumors. These data indicate that MERTK signaling in mononuclear phagocytes drives T cell regulation at inflammatory disease sites in peripheral tissues through a mechanism that reduces the sensitivity of scanning for antigen leading to reduced responsiveness to antigen.

Plasma levels of nerve growth factor in Egyptian autistic children: Relation to hyperserotonemia and autoimmunity.

Hyperserotonemia and brain-specific autoantibodies are detected in some autistic children. Nerve growth factor (NGF) stimulates the proliferation of B lymphocytes with production of antibodies and also increases mast cell serotonin release. This work was the first to investigate the relationship between plasma NGF and both hyperserotonemia and the frequency of serum anti-myelin basic protein (anti-MBP) auto-antibodies in 22 autistic children aged between 4 and 12 years and 22 healthy-matched controls. Levels of NGF, serotonin and anti-MBP were significantly higher in autistic children than healthy control children (P < 0.001). There was a significant positive correlation between NGF and serotonin levels in autistic patients (P < 0.01). In contrast, there was a non-significant correlation between NGF and anti-MBP levels (P > 0.05). In conclusions, serum NGF levels were elevated and significantly correlated to hyperserotonemia found in many autistic children.

Impact of Thyroid Autoimmunity on In Vitro Fertilization/Intracytoplasmic Sperm Injection Outcomes and Fetal Weight.

Several studies have reported the association between thyroid autoimmunity (TAI) and in vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI) outcomes. However, the findings remain controversial. We performed a large-scale retrospective cohort study to verify the effect of the presence of thyroid antibodies on IVF/ICSI outcomes and fetal growth and to evaluate the association between the types and titers of thyroid antibodies and adverse IVF/ICSI outcomes. A total of 16481 patients with infertility were referred to the Reproductive Center of Peking University Third Hospital for their first IVF/ICSI treatment between January 2018 and June 2019.Patients who sought IVF/ICSI treatment due to tubal or male factors infertility and who achieved fresh embryo transfer were included in our study. Finally, 778 patients with thyroid antibody positivity were selected as the TAI group, and 778 age-matched patients were included in the control group. The number of oocytes retrieved and high-graded embryos and the rates of clinical pregnancy, miscarriage, live birth, and preterm delivery were compared between the TAI and control groups. In addition, subgroup analysis was performed to demonstrate whether different types and titers of thyroid antibodies had different effects on IVF/ICSI outcomes. After adjusting for thyroid function, anti-Müllerian hormone levels, basal follicle stimulating hormone levels, basal estradiol levels and antral follicle count, the number of oocytes retrieved in the TAI group was significantly lower than that in the control group. No significant differences were observed between the two groups in the rates of clinical pregnancy, miscarriage, preterm delivery, live birth, and birth weight in singletons; however, the birth weight in twin pregnancy was significantly lower in the TAI group than in the control group. Subgroup analysis showed no association between the types or titers of thyroid antibodies and adverse IVF/ICSI outcomes. In conclusion, the presence of TAI in patients with infertility did not impair embryo quality or affect pregnancy outcomes, including clinical pregnancy, miscarriage, preterm delivery, and live birth. However, it decreased the number of oocytes retrieved and birth weight in twin pregnancy.

Matrine treatment induced an A2 astrocyte phenotype and protected the blood-brain barrier in CNS autoimmunity.

Type 1 astrocytes (A1), which are highly proinflammatory and neurotoxic, are prevalent in multiple sclerosis (MS). In addition, in MS and its animal model, experimental autoimmune encephalomyelitis (EAE), immune cells must cross the blood-brain barrier (BBB) and infiltrate into the parenchyma of the central nervous system (CNS) in order to induce neurological deficits. We have previously reported that treatment of EAE with matrine (MAT), a quinazine alkaloid derived from Sophorae Flavescens, effectively inhibited CNS inflammation and promoted neuroregeneration. However, the impact of MAT treatment on astrocyte phenotype is not known. In the present study, we showed that MAT treatment inhibited the generation of neurotoxic A1 astrocytes and promoted neuroprotective A2 astrocytes in the CNS of EAE, most likely by inhibiting production of the A1-inducing cytokine cocktail. MAT also downregulated the expression of vascular endothelial growth factor-A (VEGF-A) and upregulated tight junction proteins Claudin 5 and Occludin, thus protecting the BBB from CNS inflammation-induced damage. Moreover, MAT treatment promotes the formation of astrocyte tight junctions at glia limitans, thereby limiting parenchymal invasion of the CNS by immune cells. Taken together, the inhibition of A1 astrogliogenesis, and the dual effects on the BBB and astrocytic glia limitans, may be the mechanisms whereby MAT significantly improves EAE clinical scores and neuroprotection.

The role of miRNAs in the regulation of autophagy in autoimmune diseases.

Autoimmune diseases (AD), which are classified as chronic injuries, are caused by a specific auto-reactive reaction. The etiology of most ADs is not well understood. Meanwhile, Autophagy is a protective response defining as a catabolic method by lysosomes tending to maintain homeostasis acts by recycling and discrediting cell compartments. Autophagy plays a crucial role in controlling immune homeostasis by eliminating intracellular pathogens and presenting antigens to immune cognition. MicroRNAs are commonly known as endogenous non-coding small RNAs, which span 18-25 nt and take part in the gene expression at the post-transcriptional level regulation. miRNAs play important roles in different processes like, cell differentiation, duplicating, and apoptosis. Moreover, miRNAs are the critical molecules for the regular function of the immune system by modulating immune tolerance mechanisms and autoimmunity. Recent findings support the role of dysregulated miRNAs in the pathogenesis of ADs and in the regulation of autophagy. In this review, we will focus on the role of the miRNAs in the regulation of autophagy and then will explain the role of dysregulated miRNAs in the initiation of the ADs by modulating autophagy.

Insights from a Prospective Follow-up of Thyroid Function and Autoimmunity among COVID-19 Survivors.

BACKGROUND: The occurrence of Graves' disease and Hashimoto thyroiditis after coronavirus disease 2019 (COVID-19) raised concerns that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) may trigger thyroid autoimmunity. We aimed to address the current uncertainties regarding incident thyroid dysfunction and autoimmunity among COVID-19 survivors. METHODS: We included consecutive adult COVID-19 patients without known thyroid disorders, who were admitted to Queen Mary Hospital from July 21 to September 21, 2020 and had serum levels of thyroid-stimulating hormone, free thyroxine, free triiodothyronine (fT3), and anti-thyroid antibodies measured both on admission and at 3 months. RESULTS: In total, 122 patients were included. Among 20 patients with abnormal thyroid function tests (TFTs) on admission (mostly low fT3), 15 recovered. Among 102 patients with initial normal TFTs, two had new-onset abnormalities that could represent different phases of thyroiditis. Among 104 patients whose anti-thyroid antibody titers were reassessed, we observed increases in anti-thyroid peroxidase (TPO) (P<0.001) and anti-thyroglobulin (P<0.001), but not anti-thyroid stimulating hormone receptor titers (P=0.486). Of 82 patients with negative anti-TPO findings at baseline, 16 had a significant interval increase in anti-TPO titer by >12 U, and four became anti-TPO-positive. Worse baseline clinical severity (P=0.018), elevated C-reactive protein during hospitalization (P=0.033), and higher baseline anti-TPO titer (P=0.005) were associated with a significant increase in anti-TPO titer. CONCLUSION: Most patients with thyroid dysfunction on admission recovered during convalescence. Abnormal TFTs suggestive of thyroiditis occurred during convalescence, but infrequently. Importantly, our novel observation of an increase in anti-thyroid antibody titers post-COVID-19 warrants further follow-up for incident thyroid dysfunction among COVID-19 survivors.

Function, Failure, and the Future Potential of Tregs in Type 1 Diabetes.

Critical insights into the etiology of type 1 diabetes (T1D) came from genome-wide association studies that unequivocally connected genetic susceptibility to immune cell function. At the top of the susceptibility are genes involved in regulatory T-cell (Treg) function and development. The advances in epigenetic and transcriptional analyses have provided increasing evidence for Treg dysfunction in T1D. These are well supported by functional studies in mouse models and analysis of peripheral blood during T1D. For these reasons, Treg-based therapies are at the forefront of research and development and have a tangible probability to deliver a long-sought-after successful immune-targeted treatment for T1D. The current challenge in the field is whether we can directly assess Treg function at the tissue site or make informative interpretations based on peripheral data. Future studies focused on Treg function in pancreatic lymph nodes and pancreas could provide key insight into the ultimate mechanisms underlying Treg failure in T1D. In this Perspective we will provide an overview of current literature regarding Treg development and function in T1D and how this knowledge has been applied to Treg therapies.

Beneficial autoimmunity improves cancer prognosis.

Many tumour antigens that do not arise from cancer cell-specific mutations are targets of humoral and cellular immunity despite their expression on non-malignant cells. Thus, in addition to the expected ability to detect mutations and stress-associated shifts in the immunoproteome and immunopeptidome (the sum of MHC class I-bound peptides) unique to malignant cells, the immune system also recognizes antigens expressed in non-malignant cells, which can result in autoimmune reactions against non-malignant cells from the tissue of origin. These autoimmune manifestations include, among others, vitiligo, thyroiditis and paraneoplastic syndromes, concurrent with melanoma, thyroid cancer and non-small-cell lung cancer, respectively. Importantly, despite the undesirable effects of these symptoms, such events can have prognostic value and correlate with favourable disease outcomes, suggesting 'beneficial autoimmunity'. Similarly, the occurrence of dermal and endocrine autoimmune adverse events in patients receiving immune-checkpoint inhibitors can have a positive predictive value for therapeutic outcomes. Neoplasias derived from stem cells deemed 'not essential' for survival (such as melanocytes, thyroid cells and most cells in sex-specific organs) have a particularly good prognosis, perhaps because the host can tolerate autoimmune reactions that destroy tumour cells at some cost to non-malignant tissues. In this Perspective, we discuss examples of spontaneous as well as therapy-induced autoimmunity that correlate with favourable disease outcomes and make a strong case in favour of this 'beneficial autoimmunity' being important not only in patients with advanced-stage disease but also in cancer immunosurveillance.