Monogenic autoimmunity

Dietary High Salt Intake Exacerbates SGK1-Mediated T Cell Pathogenicity in L-NAME/High Salt-Induced Hypertension

Sodium chloride (NaCl) activates Th17 and dendritic cells in hypertension by stimulating serum/glucocorticoid kinase 1 (SGK1), a sodium sensor. Memory T cells also play a role in hypertension by infiltrating target organs and releasing proinflammatory cytokines. We tested the hypothesis that the role of T cell SGK1 extends to memory T cells. We employed mice with a T cell deletion of SGK1, SGK1fl/fl × tgCD4cre mice, and used SGK1fl/fl mice as controls. We treated the mice with L-NAME (0.5 mg/mL) for 2 weeks and allowed a 2-week washout interval, followed by a 3-week high-salt (HS) diet (4% NaCl). L-NAME/HS significantly increased blood pressure and memory T cell accumulation in the kidneys and bone marrow of SGK1fl/fl mice compared to knockout mice on L-NAME/HS or groups on a normal diet (ND). SGK1fl/fl mice exhibited increased albuminuria, renal fibrosis, and interferon-γ levels after L-NAME/HS treatment. Myography demonstrated endothelial dysfunction in the mesenteric arterioles of SGK1fl/fl mice. Bone marrow memory T cells were adoptively transferred from either mouse strain after L-NAME/HS administration to recipient CD45.1 mice fed the HS diet for 3 weeks. Only the mice that received cells from SGK1fl/fl donors exhibited increased blood pressure and renal memory T cell infiltration. Our data suggest a new therapeutic target for decreasing hypertension-specific memory T cells and protecting against hypertension.

The Th17/IL-17 Axis and Host Defense Against Fungal Infections

Chronic mucocutaneous candidiasis (CMC) was recognized as a primary immunodeficiency in the early 1970s. However, for almost 40 years, its genetic etiology remained unknown. The progressive molecular and cellular description of inborn errors of immunity (IEI) with syndromic CMC pointed toward a possible role of IL-17-mediated immunity in protecting against fungal infection and CMC. Since 2011, novel IEI affecting either the response to or production of IL-17A and/or IL-17F (IL-17A/F) in patients with isolated or syndromic CMC provided formal proof of the pivotal role of the IL-17 axis in mucocutaneous immunity to Candida spp, and, to a lesser extent, to Staphylococcus aureus in humans. In contrast, IL-17-mediated immunity seems largely redundant against other common microbes in humans. In this review, we outline the current knowledge of IEI associated with impaired IL-17A/F-mediated immunity, highlighting our current understanding of the role of IL-17A/F in human immunity.

Genetic susceptibility to autoimmunity-Current status and challenges

Autoimmune diseases (ADs) often arise from a combination of genetic and environmental triggers that disrupt the immune system's capability to properly tolerate body self-antigens. Familial studies provided the earliest insights into the risk loci of such diseases, while genome-wide association studies (GWAS) significantly broadened the horizons. A drug targeting a prominent pathological pathway can be applied to multiple indications sharing overlapping mechanisms. Advances in genomic technologies used in genetic studies provide critical insights into future research on gene-environment interactions in autoimmunity. This Review summarizes the history and recent advances in the understanding of genetic susceptibility to ADs and related immune disorders, including coronavirus disease 2019 (COVID-19), and their indications for the development of diagnostic or prognostic markers for translational applications.

Human autoantibodies underlying infectious diseases

The vast interindividual clinical variability observed in any microbial infection—ranging from silent infection to lethal disease—is increasingly being explained by human genetic and immunological determinants. Autoantibodies neutralizing specific cytokines underlie the same infectious diseases as inborn errors of the corresponding cytokine or response pathway. Autoantibodies against type I IFNs underlie COVID-19 pneumonia and adverse reactions to the live attenuated yellow fever virus vaccine. Autoantibodies against type II IFN underlie severe disease caused by environmental or tuberculous mycobacteria, and other intra-macrophagic microbes. Autoantibodies against IL-17A/F and IL-6 are less common and underlie mucocutaneous candidiasis and staphylococcal diseases, respectively. Inborn errors of and autoantibodies against GM-CSF underlie pulmonary alveolar proteinosis; associated infections are less well characterized. In individual patients, autoantibodies against cytokines preexist infection with the pathogen concerned and underlie the infectious disease. Human antibody-driven autoimmunity can interfere with cytokines that are essential for protective immunity to specific infectious agents but that are otherwise redundant, thereby underlying specific infectious diseases.

[Autoinflammation-A clinical and genetic challenge]

In the last two decades clinical rheumatological practice has been confronted with a steadily increasing number of autoinflammatory diseases, the immunological pathomechanisms of which have been elucidated and in part can be clinically well classified. Whereas targeted genetic diagnostics previously served to confirm a clinically suspected diagnosis, genetic sequencing technology has much improved and enables a new diagnostic approach via high-throughput sequencing, e.g., panel sequencing, whole exome and whole genome sequencing. Thus, the decision to make a diagnosis clinically and/or genetically, has become a daily challenge. This article contrasts the clinical, immunological and genetic aspects of autoinflammatory diseases.

[Autoinflammation-A clinical and genetic challenge]

In the last two decades clinical rheumatological practice has been confronted with a steadily increasing number of autoinflammatory diseases, the immunological pathomechanisms of which have been elucidated and in part can be clinically well classified. Whereas targeted genetic diagnostics previously served to confirm a clinically suspected diagnosis, genetic sequencing technology has much improved and enables a new diagnostic approach via high-throughput sequencing, e.g., panel sequencing, whole exome and whole genome sequencing. Thus, the decision to make a diagnosis clinically and/or genetically, has become a daily challenge. This article contrasts the clinical, immunological and genetic aspects of autoinflammatory diseases.

Nfkb2 variants reveal a p100-degradation threshold that defines autoimmune susceptibility

NF-κB2/p100 (p100) is an inhibitor of κB (IκB) protein that is partially degraded to produce the NF-κB2/p52 (p52) transcription factor. Heterozygous NFKB2 mutations cause a human syndrome of immunodeficiency and autoimmunity, but whether autoimmunity arises from insufficiency of p52 or IκB function of mutated p100 is unclear. Here, we studied mice bearing mutations in the p100 degron, a domain that harbors most of the clinically recognized mutations and is required for signal-dependent p100 degradation. Distinct mutations caused graded increases in p100-degradation resistance. Severe p100-degradation resistance, due to inheritance of one highly degradation-resistant allele or two subclinical alleles, caused thymic medullary hypoplasia and autoimmune disease, whereas the absence of p100 and p52 did not. We inferred a similar mechanism occurs in humans, as the T cell receptor repertoires of affected humans and mice contained a hydrophobic signature of increased self-reactivity. Autoimmunity in autosomal dominant NFKB2 syndrome arises largely from defects in nonhematopoietic cells caused by the IκB function of degradation-resistant p100.

Limosilactobacillus reuteri and Lacticaseibacillus rhamnosus GG differentially affect gut microbes and metabolites in mice with Treg deficiency

Treg deficiency causes a lethal, CD4+ T cell-driven autoimmune disease called IPEX syndrome (immunodysregulation, polyendocrinopathy, and enteropathy, with X-linked inheritance) in humans and in the scurfy (SF) mouse, a mouse model of the disease. Feeding Limosilactobacillus reuteri DSM 17938 (LR 17938, LR) to SF mice reprograms the gut microbiota, reduces disease progression, and prolongs lifespan. However, the efficacy and mechanism of LR, compared with other probiotics, in producing these effects is unknown. We compared LR with Lacticaseibacillus rhamnosus GG (LGG), an extensively investigated probiotic. LR was more effective than LGG in prolonging survival. Both probiotics restored the fecal microbial alpha diversity, but they produced distinct fecal bacterial clusters and differentially modulated microbial relative abundance (RA). LR increased the RA of phylum_Firmicutes, genus_Oscillospira whereas LR reduced phylum_Bacteroidetes, genus_Bacteroides and genus_Parabacteroides, reversing changes attributed to the SF phenotype. LGG primarily reduced the RA of genus_Bacteroides. Both LR and LGG reduced the potentially pathogenic taxon class_γ-proteobacteria. Plasma metabolomics revealed substantial differences among 696 metabolites. We observed similar changes of many clusters of metabolites in SF mice associated with treatment with either LR or LGG. However, a unique effect of LR was to increase the abundance of plasma adenosine metabolites such as inosine, which we previously showed had immune modulatory effects. In conclusion: 1) different probiotics produce distinct signatures in the fecal microbial community in mice with Treg deficiency; and 2) when comparing different probiotics, there are strain-specific microbial products with different anti-inflammatory properties, reinforcing the concept that "one size does not fit all" in the treatment of autoimmune disease.NEW & NOTEWORTHY In the treatment of Treg-deficiency-induced autoimmunity, Limosilactobacillus reuteri DSM 17938 (LR) showed greater efficacy than Lacticaseibacillus rhamnosus GG (LGG). The study demonstrated that two different probiotics produce distinct signatures in the fecal microbial community in mice with Treg deficiency, but with many similarities in global plasma metabolites in general. However, there are strain-specific microbial products with different anti-inflammatory properties, reinforcing the concept that "one size does not fit all" in the treatment of autoimmune disease.

Development of double-positive thymocytes at single-cell resolution

BACKGROUND

T cells generated from thymopoiesis are essential for the immune system, and recent single-cell studies have contributed to our understanding of the development of thymocytes at the genetic and epigenetic levels. However, the development of double-positive (DP) T cells, which comprise the majority of thymocytes, has not been well investigated.

METHODS

We applied single-cell sequencing to mouse thymocytes and analyzed the transcriptome data using Seurat. By applying unsupervised clustering, we defined thymocyte subtypes and validated DP cell subtypes by flow cytometry. We classified the cell cycle phases of each cell according to expression of cell cycle phase-specific genes. For immune synapse detection, we used immunofluorescent staining and ImageStream-based flow cytometry. We studied and integrated human thymocyte data to verify the conservation of our findings and also performed cross-species comparisons to examine species-specific gene regulation.

RESULTS

We classified blast, rearrangement, and selection subtypes of DP thymocytes and used the surface markers CD2 and Ly6d to identify these subtypes by flow cytometry. Based on this new classification, we found that the proliferation of blast DP cells is quite different from that of double-positive cells and other cell types, which tend to exit the cell cycle after a single round. At the DP cell selection stage, we observed that CD8-associated immune synapses formed between thymocytes, indicating that CD8sp selection occurred among thymocytes themselves. Moreover, cross-species comparison revealed species-specific transcription factors (TFs) that contribute to the transcriptional differences of thymocytes from humans and mice.

CONCLUSIONS

Our study classified DP thymocyte subtypes of different developmental stages and provided new insight into the development of DP thymocytes at single-cell resolution, furthering our knowledge of the fundamental immunological process of thymopoiesis.

Follicular regulatory T cells produce neuritin to regulate B cells

Regulatory T cells prevent the emergence of autoantibodies and excessive IgE, but the precise mechanisms are unclear. Here, we show that BCL6-expressing Tregs, known as follicular regulatory T (Tfr) cells, produce abundant neuritin protein that targets B cells. Mice lacking Tfr cells or neuritin in Foxp3-expressing cells accumulated early plasma cells in germinal centers (GCs) and developed autoantibodies against histones and tissue-specific self-antigens. Upon immunization, these mice also produced increased plasma IgE and IgG1. We show that neuritin is taken up by B cells, causes phosphorylation of numerous proteins, and dampens IgE class switching. Neuritin reduced differentiation of mouse and human GC B cells into plasma cells, downregulated BLIMP-1, and upregulated BCL6. Administration of neuritin to Tfr-deficient mice prevented the accumulation of early plasma cells in GCs. Production of neuritin by Tfr cells emerges as a central mechanism to suppress B cell-driven autoimmunity and IgE-mediated allergies.

The conserved autoimmune-disease risk gene TMEM39A regulates lysosome dynamics

TMEM39A encodes an evolutionarily conserved transmembrane protein and carries single-nucleotide polymorphisms associated with increased risk of major human autoimmune diseases, including multiple sclerosis. The exact cellular function of TMEM39A remains not well understood. Here, we report that TMEM-39, the sole Caenorhabditis elegans (C. elegans) ortholog of TMEM39A, regulates lysosome distribution and accumulation. Elimination of tmem-39 leads to lysosome tubularization and reduced lysosome mobility, as well as accumulation of the lysosome-associated membrane protein LMP-1. In mammalian cells, loss of TMEM39A leads to redistribution of lysosomes from the perinuclear region to cell periphery. Mechanistically, TMEM39A interacts with the dynein intermediate light chain DYNC1I2 to maintain proper lysosome distribution. Deficiency of tmem-39 or the DYNC1I2 homolog in C. elegans impairs mTOR signaling and activates the downstream TFEB-like transcription factor HLH-30. We propose evolutionarily conserved roles of TMEM39 family proteins in regulating lysosome distribution and lysosome-associated signaling, dysfunction of which in humans may underlie aspects of autoimmune diseases.

Immune response of Brazilian farmers exposed to multiple pesticides

Occupational exposure to pesticides has been identified as a factor that predisposes to disorders of the immune system. Immunosuppression, autoimmunity, cancer of various organs and other diseases in people who apply these products have been reported by the studies. This study aimed to investigate the relationship between occupational exposure to pesticides and the immunological profile in 43 farmers exposed to mixtures of pesticides for at least 15 years. A control group composed of 30 individuals without a history of occupational exposure to pesticides was also evaluated. Peripheral blood samples were processed by flow cytometry and cells were labelled with an 8-color monoclonal antibody panel. Plasma cytokines were also measured. Significant increase in classical monocytes (p < 0.001) and dendritic cells (p < 0.001) in the exposed group was observed as well in total T cells (p = 0.04), central memory CD8 T cells (p = 0.02) and effector memory CD8 T cells (p = 0.01). On the other hand, the activation markers of T cells as the expression of CD57, HLA-DR, CD25 and CD28 were evaluated and no difference was found between groups. When the B cells were analyzed, a significant decrease in total B cells (p = 0.01), regulatory B cells (p < 0.001) and plasmablasts (p < 0.001) in the exposed group, compared to healthy controls, was observed. Pro-inflammatory IL-6 was significantly elevated (p = 0.04) in the plasma of farmers compared to that of controls. The constant antigenic stimulus that occurs during exposure to pesticides can favor the recruitment of dendritic cells and macrophages (APCs) presents in the skin and respiratory tract. In the secondary lymphoid organs, the CD4 T and B cells that process such antigens are possibly undergoing proliferative exhaustion, with the consequent depletion of all mature B subpopulations. The resulting drop in humoral immunity may be offset by an increase in the number of circulating CD8 T lymphocytes due to their cytotoxic action.

Decreased Foxp3 and function of Tregs caused immune imbalance and liver injury in patients with autoimmune liver diseases post-liver transplantation

Background

Autoimmune liver diseases (AILD) is a type of autoimmune disease which may cause end-stage liver failure and require liver transplantation. Regulatory T cells (Tregs) play an irreplaceable role in maintaining immunological homeostasis.

Methods

In this study, we made a comparative analysis of the immune balance and graft function between AILD patients’ post-transplantation and the patients who have had liver failure with hepatitis B virus (HBV) infection post-transplantation. Immune cell phenotype of two groups were analyzed. We sorted CD4+CD25+CD127-Tregs both in vitro and vivo and did TSDR methylation status assay to explore further possible mechanisms.

Results

Our data showed that there is a worse prognosis with severe graft function in liver transplant patients with AILD compared to patients with HBV-induced liver failure. Immune cell phenotype analysis showed that more Tregs could be detected in AILD patients compared with HBV patients’ post-transplantation. We sorted CD4+CD25+CD127-Tregs in vivo and showed that Tregs presented decreased function both in vitro and vivo. Mechanism study also proved that modulation of the phosphorylation level of STAT1 and STAT3 as well as the methylation level of TSDR in Foxp3 might partially result in the function loss of Tregs.

Conclusions

These results suggest that loss of Foxp3 expression and suppressive function of Tregs may be the critical factor that causes graft loss for liver transplant patients after AILD.

Understanding the immunopathogenesis of autoimmune diseases by animal studies using gene modulation: A comprehensive review

Autoimmune diseases are clinical syndromes that result from pathogenic inflammatory responses driven by inadequate immune activation by T- and B-cells. Although the exact mechanisms of autoimmune diseases are still elusive, genetic factors also play an important role in the pathogenesis. Recently, with the advancement of understanding of the immunological and molecular basis of autoimmune diseases, gene modulation has become a potential approach for the tailored treatment of autoimmune disorders. Gene modulation can be applied to regulate the levels of interleukins (IL), tumor necrosis factor (TNF), cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4), interferon-γ and other inflammatory cytokines by inhibiting these cytokine expressions using short interfering ribonucleic acid (siRNA) or by inhibiting cytokine signaling using small molecules. In addition, gene modulation delivering anti-inflammatory cytokines or cytokine antagonists showed effectiveness in regulating autoimmunity. In this review, we summarize the potential target genes for gene or immunomodulation in autoimmune diseases including rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), inflammatory bowel diseases (IBD) and multiple sclerosis (MS). This article will give a new perspective on understanding immunopathogenesis of autoimmune diseases not only in animals but also in human. Emerging approaches to investigate cytokine regulation through gene modulation may be a potential approach for the tailored immunomodulation of some autoimmune diseases near in the future.

Zero tolerance! A perspective on monogenic disorders with defective regulatory T cells and IBD-like disease

Recently, several studies have investigated a number of rare monogenic autoimmune disorders, in which the causative genetic defects were identified and found to affect the development or function of regulatory T cells (Tregs). The studies of these disorders have facilitated a deeper understanding of the mechanisms involved in immune regulation and tolerance. Furthermore, these studies have highlighted the importance of Tregs in maintaining homeostasis at the mucosal interface between the host and microbiome. Here, we offer our perspective on these monogenic autoimmune disorders, highlighting their overlapping clinical features with inflammatory bowel disease.

Type I interferons and endoplasmic reticulum stress in health and disease

Type I interferons (IFNs) comprise of pro-inflammatory cytokines created, as well as sensed, by all nucleated cells with the main objective of blocking pathogens-driven infections. Owing to this broad range of influence, type I IFNs also exhibit critical functions in many sterile inflammatory diseases and immunopathologies, especially those associated with endoplasmic reticulum (ER) stress-driven signaling pathways. Indeed, over the years accumulating evidence has indicated that the presence of ER stress can influence the production, or sensing of, type I IFNs induced by perturbations like pattern recognition receptor (PRR) agonists, infections (bacterial, viral or parasitic) or autoimmunity. In this article we discuss the link between type I IFNs and ER stress in various diseased contexts. We describe how ER stress regulates type I IFNs production or sensing, or how type I IFNs may induce ER stress, in various circumstances like microbial infections, autoimmunity, diabetes, cancer and other ER stress-related contexts.

TCR Retrogenic Mice as a Model To Map Self-Tolerance Mechanisms to the Cancer Mucosa Antigen GUCY2C

Characterizing self-tolerance mechanisms and their failure is critical to understand immune homeostasis, cancer immunity, and autoimmunity. However, examination of self-tolerance mechanisms has relied primarily on transgenic mice expressing TCRs targeting well-characterized, but nonphysiologic, model Ags, such as OVA and hemagglutinin. Identifying TCRs directed against bona fide self-antigens is made difficult by the extraordinary diversity of TCRs and the low prevalence of Ag-specific clones (<10-100 naive cells per organism), limiting dissection of tolerance mechanisms restricting immunity to self-proteins. In this study, we isolated and characterized TCRs recognizing the intestinal epithelial cell receptor and colorectal cancer Ag GUCY2C to establish a model to study self-antigen-specific tolerance mechanisms. GUCY2C-specific CD4+ effector T cells were isolated from immunized, nontolerant Gucy2c -/- mice. Next-generation sequencing identified GUCY2C-specific TCRs, which were engineered into CD4+ T cells in vitro to confirm TCR recognition of GUCY2C. Further, the generation of "retrogenic" mice by reconstitution with TCR-transduced hematopoietic stem cells resulted in normal CD4+ T cell development, responsiveness to immunization, and GUCY2C-induced tolerance in recipient mice, recapitulating observations in conventional models. This retrogenic model can be employed to define self-tolerance mechanisms restricting T and B cell responses to GUCY2C to optimize colorectal cancer immunotherapy without autoimmunity.

Genetic and epigenetic influences on the loss of tolerance in autoimmunity

Immunological tolerance loss is fundamental to the development of autoimmunity; however, the underlying mechanisms remain elusive. Immune tolerance consists of central and peripheral tolerance. Central tolerance, which occurs in the thymus for T cells and bone marrow for B cells, is the primary way that the immune system discriminates self from non-self. Peripheral tolerance, which occurs in tissues and lymph nodes after lymphocyte maturation, controls self-reactive immune cells and prevents over-reactive immune responses to various environment factors. Loss of tolerance results in autoimmune disorders, such as systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), type 1 diabetes (T1D) and primary biliary cirrhosis (PBC). The etiology and pathogenesis of autoimmune diseases are highly complicated. Both genetic predisposition and epigenetic modifications are implicated in the loss of tolerance and autoimmunity. In this review, we will discuss the genetic and epigenetic influences on tolerance breakdown in autoimmunity. Genetic and epigenetic influences on autoimmune diseases, such as SLE, RA, T1D and PBC, will also be briefly discussed.

Insights into immune tolerance from AIRE deficiency

AIRE is a well-established master regulator of central tolerance. It plays an essential role in driving expression of tissue-specific antigens in the thymus and shaping the development of positively selected T-cells. Humans and mice with compromised or absent AIRE function have markedly variable phenotypes that include a range of autoimmune manifestations. Recent evidence suggests that this variability stems from cooperation of autoimmune susceptibilities involving both central and peripheral tolerance checkpoints. Here we discuss the broadening understanding of the factors that influence Aire expression, modify AIRE function, and the impact and intersection of AIRE with peripheral immunity. This rapidly expanding body of knowledge will force a reexamination of the definition and clinical management of APS-1 patients as well as provide a foundation for the development of immunomodulatory strategies targeting central tolerance.

Checkpoint Blockade Toxicity and Immune Homeostasis in the Gastrointestinal Tract

Monoclonal antibodies targeting the regulatory immune "checkpoint" receptors CTLA-4, PD-1, and PD-L1 are now standard therapy for diverse malignancies including melanoma, lung cancer, and renal cell carcinoma. Although effective in many patients and able to induce cures in some, targeting these regulatory pathways has led to a new class of immune-related adverse events. In many respects, these immune toxicities resemble idiopathic autoimmune diseases, such as inflammatory bowel disease, autoimmune hepatitis, rheumatoid arthritis, and vitiligo. Understanding the pathogenesis of these immune toxicities will have implications not only for care of patients receiving checkpoint blockade but may also provide critical insights into autoimmune disease. The gastrointestinal (GI) mucosa is arguably the most complex barrier in the body, host to a diverse commensal microflora and constantly challenged by ingested foreign proteins both of which must be tolerated. At the same time, the GI mucosa must defend against pathogenic microorganisms while maintaining sufficient permeability to absorb nutrients. For these reasons, regulatory cells and receptors are likely to play a central role in maintaining the gut barrier and GI toxicities, such as colitis and hepatitis are indeed among the most common side effects of CTLA-4 blockade and to a lesser extent blockade of PD-1 and PD-L1. High-dose corticosteroids are typically effective for management of both checkpoint colitis and hepatitis, although a fraction of patients will require additional immune suppression such as infliximab. Prompt recognition and treatment of these toxicities is essential to prevent more serious complications.

Autoimmune aspects of psoriasis: Heritability and autoantigens

Chronic immune-mediated disorders (IMDs) constitute a major health burden. Understanding IMD pathogenesis is facing two major constraints: Missing heritability explaining familial clustering, and missing autoantigens. Pinpointing IMD risk genes and autoimmune targets, however, is of fundamental importance for developing novel causal therapies. The strongest association of all IMDs is seen with human leukocyte antigen (HLA) alleles. Using psoriasis as an IMD model this article reviews the pathogenic role HLA molecules may have within the polygenic predisposition of IMDs. It concludes that disease-associated HLA alleles account for both missing heritability and autoimmune mechanisms by facilitating tissue-specific autoimmune responses through autoantigen presentation.

Primary immunodeficiencies suggest redundancy within the human immune system

Pathogen-driven evolution has shaped the complexity of the human immune system. Our genome contains at least 1854 gene products involved in immune responses. However, the redundancy and robustness of the immune system need further characterization. One way to examine this redundancy is through the study of monogenic primary immunodeficiencies (PIDs) associated with infections. Causal mutations affecting innate immunity genes are, in relative terms, close to seven times less frequent than those affecting adaptive immunity genes in PIDs. Loss-of-function mutations of innate immunity genes encoding pattern-recognition receptors (PRRs) and associated pathways rarely cause susceptibility to infections, which suggests that PRR pathways are partially redundant in the immune responses to infection. This dispensability has also been observed for constitutive products of the immune system, such as secretory immunoglobulin A, and for innate immune cells, such as natural killer and innate lymphoid cell subsets, which are not essential for viability. This Review discusses these findings in the context of their implications for the identification of previously unknown classes of PIDs and assessment of the susceptibility to infection associated with various targeted immunotherapies.

Rare phenotypes in the understanding of autoimmunity

The study of rare phenotypes has a long history in the description of autoimmune disorders. First Mendelian syndromes of idiopathic tissue destruction were defined more than 100 years ago and were later revealed to result from immune-mediated reactivity against self. In the past two decades, continuous advances in sequencing technology and particularly the advent of next-generation sequencing have allowed to define the genetic basis of an ever-growing number of Mendelian forms of autoimmunity. This has provided unique insight into the molecular pathways that govern immunological homeostasis and that are indispensable for the prevention of self-reactive immune-mediated tissue damage and 'horror autotoxicus'. Here we will discuss selected examples of past and recent investigations into rare phenotypes of autoimmunity that have delineated pathways critical for central and peripheral control of the adaptive immune system. We will outline the implications of these findings for rare and common forms of autoimmunity and will discuss the benefits and potential pitfalls of the integration of next-generation sequencing into algorithms for clinical diagnostics. Because of the concise nature of this review, we will focus on syndromes caused by defects in the control of adaptive immunity as innate immune-mediated autoinflammatory disorders have been covered in excellent recent reviews on Mendelian and polygenic forms of autoimmunity.

Germinal centers and autoimmune disease in humans and mice

Antibodies are involved in the pathogenesis of many autoimmune diseases. Although the mechanisms underlying the antibody response to infection or vaccination are reasonably well understood, we still have a poor understanding of the nature of autoimmune antibody responses. The most well studied are the anti-nuclear antibody responses characteristic of systemic lupus erythematosus and studies over the past decade or so have demonstrated a critical role for signaling by TLR7 and/or TLR9 in B cells to promote these responses. These Toll-like receptors (TLRs) can promote T-cell-independent extrafollicular antibody responses with a heavy-chain class switch and a low degree of somatic mutation, but they can also strongly boost the germinal center response that gives rise to high-affinity antibodies and long-lived plasma cells. TLRs have been shown to enhance affinity maturation in germinal center responses to produce high-affinity neutralizing antibodies in several virus infection models of mice. Although more data are needed, it appears that anti-nuclear antibodies in mouse models of lupus and in lupus patients can be generated by either pathway, provided there are genetic susceptibility alleles that compromise B-cell tolerance at one or another stage. Limited data in other autoimmune diseases suggest that the germinal center response may be the predominant pathway leading to autoantibodies in those diseases. A better understanding of the mechanisms of autoantibody production may ultimately be helpful in the development of targeted therapeutics for lupus or other autoimmune diseases.

Heterozygous STAT1 gain-of-function mutations underlie an unexpectedly broad clinical phenotype

Since their discovery in patients with autosomal dominant (AD) chronic mucocutaneous candidiasis (CMC) in 2011, heterozygous STAT1 gain-of-function (GOF) mutations have increasingly been identified worldwide. The clinical spectrum associated with them needed to be delineated. We enrolled 274 patients from 167 kindreds originating from 40 countries from 5 continents. Demographic data, clinical features, immunological parameters, treatment, and outcome were recorded. The median age of the 274 patients was 22 years (range, 1-71 years); 98% of them had CMC, with a median age at onset of 1 year (range, 0-24 years). Patients often displayed bacterial (74%) infections, mostly because of Staphylococcus aureus (36%), including the respiratory tract and the skin in 47% and 28% of patients, respectively, and viral (38%) infections, mostly because of Herpesviridae (83%) and affecting the skin in 32% of patients. Invasive fungal infections (10%), mostly caused by Candida spp. (29%), and mycobacterial disease (6%) caused by Mycobacterium tuberculosis, environmental mycobacteria, or Bacille Calmette-Guérin vaccines were less common. Many patients had autoimmune manifestations (37%), including hypothyroidism (22%), type 1 diabetes (4%), blood cytopenia (4%), and systemic lupus erythematosus (2%). Invasive infections (25%), cerebral aneurysms (6%), and cancers (6%) were the strongest predictors of poor outcome. CMC persisted in 39% of the 202 patients receiving prolonged antifungal treatment. Circulating interleukin-17A-producing T-cell count was low for most (82%) but not all of the patients tested. STAT1 GOF mutations underlie AD CMC, as well as an unexpectedly wide range of other clinical features, including not only a variety of infectious and autoimmune diseases, but also cerebral aneurysms and carcinomas that confer a poor prognosis.

AIRE is not essential for the induction of human tolerogenic dendritic cells

Loss-of-function mutations of the Autoimmune Regulator (AIRE) gene results in organ-specific autoimmunity and disease Autoimmune Polyendocrinopathy type 1 (APS1)/Autoimmune Polyendocrinopathy Candidiasis Ectodermal Dystrophy (APECED). The AIRE protein is crucial in the induction of central tolerance, promoting ectopic expression of tissue-specific antigens in medullary thymic epithelial cells and enabling removal of self-reactive T-cells. AIRE expression has recently been detected in myeloid dendritic cells (DC), suggesting AIRE may have a significant role in peripheral tolerance. DC stimulation of T-cells is critical in determining the initiation or lack of an immune response, depending on the pattern of costimulation and cytokine production by DCs, defining immunogenic/inflammatory (inflDC) and tolerogenic (tolDC) DC. In AIRE-deficient patients and healthy controls, we validated the role of AIRE in the generation and function of monocyte-derived inflDC and tolDCs by determining mRNA and protein expression of AIRE and comparing activation markers (HLA-DR/DP/DQ,CD83,CD86,CD274(PDL-1),TLR-2), cytokine production (IL-12p70,IL-10,IL-6,TNF-α,IFN-γ) and T-cell stimulatory capacity (mixed lymphocyte reaction) of AIRE+ and AIRE- DCs. We show for the first time that: (1) tolDCs from healthy individuals express AIRE; (2) AIRE expression is not significantly higher in tolDC compared to inflDC; (3) tolDC can be generated from APECED patient monocytes and (4) tolDCs lacking AIRE retain the same phenotype and reduced T-cell stimulatory function. Our findings suggest that AIRE does not have a role in the induction and function of monocyte-derived tolerogenic DC in humans, but these findings do not exclude a role for AIRE in peripheral tolerance mediated by other cell types.

Heterozygous STAT1 gain-of-function mutations underlie an unexpectedly broad clinical phenotype

Since their discovery in patients with autosomal dominant (AD) chronic mucocutaneous candidiasis (CMC) in 2011, heterozygous STAT1 gain-of-function (GOF) mutations have increasingly been identified worldwide. The clinical spectrum associated with them needed to be delineated. We enrolled 274 patients from 167 kindreds originating from 40 countries from 5 continents. Demographic data, clinical features, immunological parameters, treatment, and outcome were recorded. The median age of the 274 patients was 22 years (range, 1-71 years); 98% of them had CMC, with a median age at onset of 1 year (range, 0-24 years). Patients often displayed bacterial (74%) infections, mostly because of Staphylococcus aureus (36%), including the respiratory tract and the skin in 47% and 28% of patients, respectively, and viral (38%) infections, mostly because of Herpesviridae (83%) and affecting the skin in 32% of patients. Invasive fungal infections (10%), mostly caused by Candida spp. (29%), and mycobacterial disease (6%) caused by Mycobacterium tuberculosis, environmental mycobacteria, or Bacille Calmette-Guérin vaccines were less common. Many patients had autoimmune manifestations (37%), including hypothyroidism (22%), type 1 diabetes (4%), blood cytopenia (4%), and systemic lupus erythematosus (2%). Invasive infections (25%), cerebral aneurysms (6%), and cancers (6%) were the strongest predictors of poor outcome. CMC persisted in 39% of the 202 patients receiving prolonged antifungal treatment. Circulating interleukin-17A-producing T-cell count was low for most (82%) but not all of the patients tested. STAT1 GOF mutations underlie AD CMC, as well as an unexpectedly wide range of other clinical features, including not only a variety of infectious and autoimmune diseases, but also cerebral aneurysms and carcinomas that confer a poor prognosis.

AIRE expands: new roles in immune tolerance and beyond

More than 15 years ago, mutations in the autoimmune regulator (AIRE) gene were identified as the cause of autoimmune polyglandular syndrome type 1 (APS1). It is now clear that this transcription factor has a crucial role in promoting self-tolerance in the thymus by regulating the expression of a wide array of self-antigens that have the commonality of being tissue-restricted in their expression pattern in the periphery. In this Review, we highlight many of the recent advances in our understanding of the complex biology that is related to AIRE, with a particular focus on advances in genetics, molecular interactions and the effect of AIRE on thymic selection of regulatory T cells. Furthermore, we highlight new areas of biology that are potentially affected by this key regulator of immune tolerance.

Personalized Immunomonitoring Uncovers Molecular Networks that Stratify Lupus Patients

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by loss of tolerance to nucleic acids and highly diverse clinical manifestations. To assess its molecular heterogeneity, we longitudinally profiled the blood transcriptome of 158 pediatric patients. Using mixed models accounting for repeated measurements, demographics, treatment, disease activity (DA), and nephritis class, we confirmed a prevalent IFN signature and identified a plasmablast signature as the most robust biomarker of DA. We detected gradual enrichment of neutrophil transcripts during progression to active nephritis and distinct signatures in response to treatment in different nephritis subclasses. Importantly, personalized immunomonitoring uncovered individual correlates of disease activity that enabled patient stratification into seven groups, supported by patient genotypes. Our study uncovers the molecular heterogeneity of SLE and provides an explanation for the failure of clinical trials. This approach may improve trial design and implementation of tailored therapies in genetically and clinically complex autoimmune diseases. PAPERCLIP.

More than Meets the Eye: Monogenic Autoimmunity Strikes Again

Autoimmunity is often familial, suggesting that inborn genetic variations might underlie its development. Curiously, autoimmunity has long been thought to be typically polygenic. Contrary to this prediction and consistent with growing discoveries of monogenic autoimmunity, Oftedal et al. discovered heterozygous dominant-negative AIRE mutations in patients with certain forms of autoimmunity.

Transglutaminase 4 as a prostate autoantigen in male subfertility

Autoimmune polyendocrine syndrome type 1 (APS1), a monogenic disorder caused by AIRE gene mutations, features multiple autoimmune disease components. Infertility is common in both males and females with APS1. Although female infertility can be explained by autoimmune ovarian failure, the mechanisms underlying male infertility have remained poorly understood. We performed a proteome-wide autoantibody screen in APS1 patient sera to assess the autoimmune response against the male reproductive organs. By screening human protein arrays with male and female patient sera and by selecting for gender-imbalanced autoantibody signals, we identified transglutaminase 4 (TGM4) as a male-specific autoantigen. Notably, TGM4 is a prostatic secretory molecule with critical role in male reproduction. TGM4 autoantibodies were detected in most of the adult male APS1 patients but were absent in all the young males. Consecutive serum samples further revealed that TGM4 autoantibodies first presented during pubertal age and subsequent to prostate maturation. We assessed the animal model for APS1, the Aire-deficient mouse, and found spontaneous development of TGM4 autoantibodies specifically in males. Aire-deficient mice failed to present TGM4 in the thymus, consistent with a defect in central tolerance for TGM4. In the mouse, we further link TGM4 immunity with a destructive prostatitis and compromised secretion of TGM4. Collectively, our findings in APS1 patients and Aire-deficient mice reveal prostate autoimmunity as a major manifestation of APS1 with potential role in male subfertility.

Genetic basis of autoimmunity

Autoimmune diseases affect up to approximately 10% of the population. While rare Mendelian autoimmunity syndromes can result from monogenic mutations disrupting essential mechanisms of central and peripheral tolerance, more common human autoimmune diseases are complex disorders that arise from the interaction between polygenic risk factors and environmental factors. Although the risk attributable to most individual nucleotide variants is modest, genome-wide association studies (GWAS) have the potential to provide an unbiased view of biological pathways that drive human autoimmune diseases. Interpretation of GWAS requires integration of multiple genomic datasets including dense genotyping, cis-regulatory maps of primary immune cells, and genotyped studies of gene expression in relevant cell types and cellular conditions. Improved understanding of the genetic basis of autoimmunity may lead to a more sophisticated understanding of underlying cellular phenotypes and, eventually, novel diagnostics and targeted therapies.

T cells in the control of organ-specific autoimmunity

Immune tolerance is critical to the avoidance of unwarranted immune responses against self antigens. Multiple, non-redundant checkpoints are in place to prevent such potentially deleterious autoimmune responses while preserving immunity integral to the fight against foreign pathogens. Nevertheless, a large and growing segment of the population is developing autoimmune diseases. Deciphering cellular and molecular pathways of immune tolerance is an important goal, with the expectation that understanding these pathways will lead to new clinical advances in the treatment of these devastating diseases. The vast majority of autoimmune diseases develop as a consequence of complex mechanisms that depend on genetic, epigenetic, molecular, cellular, and environmental elements and result in alterations in many different checkpoints of tolerance and ultimately in the breakdown of immune tolerance. The manifestations of this breakdown are harmful inflammatory responses in peripheral tissues driven by innate immunity and self antigen-specific pathogenic T and B cells. T cells play a central role in the regulation and initiation of these responses. In this Review we summarize our current understanding of the mechanisms involved in these fundamental checkpoints, the pathways that are defective in autoimmune diseases, and the therapeutic strategies being developed with the goal of restoring immune tolerance.

COPA mutations impair ER-Golgi transport and cause hereditary autoimmune-mediated lung disease and arthritis

Unbiased genetic studies have uncovered surprising molecular mechanisms in human cellular immunity and autoimmunity. We performed whole-exome sequencing and targeted sequencing in five families with an apparent mendelian syndrome of autoimmunity characterized by high-titer autoantibodies, inflammatory arthritis and interstitial lung disease. We identified four unique deleterious variants in the COPA gene (encoding coatomer subunit α) affecting the same functional domain. Hypothesizing that mutant COPA leads to defective intracellular transport via coat protein complex I (COPI), we show that COPA variants impair binding to proteins targeted for retrograde Golgi-to-ER transport. Additionally, expression of mutant COPA results in ER stress and the upregulation of cytokines priming for a T helper type 17 (TH17) response. Patient-derived CD4(+) T cells also demonstrate significant skewing toward a TH17 phenotype that is implicated in autoimmunity. Our findings uncover an unexpected molecular link between a vesicular transport protein and a syndrome of autoimmunity manifested by lung and joint disease.

A brief history of T cell help to B cells

In celebration of the 50th anniversary of the discovery of B cells, I take a look back at the history of T cell help to B cells, which was discovered 47 years ago. In addition, I summarize and categorize the distinct molecules that are expressed by CD4(+) T cells that constitute 'help' to B cells, and particularly the molecules expressed by T follicular helper (TFH) cells, which are the specialized providers of help to B cells.

Type 1 diabetes and polyglandular autoimmune syndrome: A review

Type 1 diabetes (T1D) is an autoimmune disorder caused by inflammatory destruction of the pancreatic tissue. The etiopathogenesis and characteristics of the pathologic process of pancreatic destruction are well described. In addition, the putative susceptibility genes for T1D as a monoglandular disease and the relation to polyglandular autoimmune syndrome (PAS) have also been well explored. The incidence of T1D has steadily increased in most parts of the world, especially in industrialized nations. T1D is frequently associated with autoimmune endocrine and non-endocrine diseases and patients with T1D are at a higher risk for developing several glandular autoimmune diseases. Familial clustering is observed, which suggests that there is a genetic predisposition. Various hypotheses pertaining to viral- and bacterial-induced pancreatic autoimmunity have been proposed, however a definitive delineation of the autoimmune pathomechanism is still lacking. In patients with PAS, pancreatic and endocrine autoantigens either colocalize on one antigen-presenting cell or are expressed on two/various target cells sharing a common amino acid, which facilitates binding to and activation of T cells. The most prevalent PAS phenotype is the adult type 3 variant or PAS type III, which encompasses T1D and autoimmune thyroid disease. This review discusses the findings of recent studies showing noticeable differences in the genetic background and clinical phenotype of T1D either as an isolated autoimmune endocrinopathy or within the scope of polyglandular autoimmune syndrome.

Early-onset lymphoproliferation and autoimmunity caused by germline STAT3 gain-of-function mutations

Germline loss-of-function mutations in the transcription factor signal transducer and activator of transcription 3 (STAT3) cause immunodeficiency, whereas somatic gain-of-function mutations in STAT3 are associated with large granular lymphocytic leukemic, myelodysplastic syndrome, and aplastic anemia. Recently, germline mutations in STAT3 have also been associated with autoimmune disease. Here, we report on 13 individuals from 10 families with lymphoproliferation and early-onset solid-organ autoimmunity associated with 9 different germline heterozygous mutations in STAT3. Patients exhibited a variety of clinical features, with most having lymphadenopathy, autoimmune cytopenias, multiorgan autoimmunity (lung, gastrointestinal, hepatic, and/or endocrine dysfunction), infections, and short stature. Functional analyses demonstrate that these mutations confer a gain-of-function in STAT3 leading to secondary defects in STAT5 and STAT1 phosphorylation and the regulatory T-cell compartment. Treatment targeting a cytokine pathway that signals through STAT3 led to clinical improvement in 1 patient, suggesting a potential therapeutic option for such patients. These results suggest that there is a broad range of autoimmunity caused by germline STAT3 gain-of-function mutations, and that hematologic autoimmunity is a major component of this newly described disorder. Some patients for this study were enrolled in a trial registered at www.clinicaltrials.gov as #NCT00001350.

Autoimmune predisposition in Down syndrome may result from a partial central tolerance failure due to insufficient intrathymic expression of AIRE and peripheral antigens

Down syndrome (DS), or trisomy of chromosome 21, is the most common genetic disorder associated with autoimmune diseases. Autoimmune regulator protein (AIRE), a transcription factor located on chromosome 21, plays a crucial role in autoimmunity by regulating promiscuous gene expression (pGE). To investigate if autoimmunity in DS is promoted by the reduction of pGE owing to dysregulation of AIRE, we assessed the expression of AIRE and of several peripheral tissue-restricted Ag genes by quantitative PCR in thymus samples from 19 DS subjects and 21 euploid controls. Strikingly, despite the 21 trisomy, AIRE expression was significantly reduced by 2-fold in DS thymuses compared with controls, which was also confirmed by fluorescent microscopy. Allele-specific quantification of intrathymic AIRE showed that despite its lower expression, the three copies are expressed. More importantly, decreased expression of AIRE was accompanied by a reduction of pGE because expression of tissue-restricted Ags, CHRNA1, GAD1, PLP1, KLK3, SAG, TG, and TSHR, was reduced. Of interest, thyroid dysfunction (10 cases of hypothyroidism and 1 of Graves disease) developed in 11 of 19 (57.9%) of the DS individuals and in none of the 21 controls. The thymuses of these DS individuals contained significantly lower levels of AIRE and thyroglobulin, to which tolerance is typically lost in autoimmune thyroiditis leading to hypothyroidism. Our findings provide strong evidence for the fundamental role of AIRE and pGE, namely, central tolerance, in the predisposition to autoimmunity of DS individuals.

Selective antigen-specific CD4(+) T-cell, but not CD8(+) T- or B-cell, tolerance corrupts cancer immunotherapy

Self-tolerance, presumably through lineage-unbiased elimination of self-antigen-specific lymphocytes (CD4(+) T, CD8(+) T, and B cells), creates a formidable barrier to cancer immunotherapy. In contrast to this prevailing paradigm, we demonstrate that for some antigens, self-tolerance reflects selective elimination of antigen-specific CD4(+) T cells, but preservation of CD8(+) T- and B-cell populations. In mice, antigen-specific CD4(+) T-cell tolerance restricted CD8(+) T- and B-cell responses targeting the endogenous self-antigen guanylyl cyclase c (GUCY2C) in colorectal cancer. Although selective CD4(+) T-cell tolerance blocked GUCY2C-specific antitumor immunity and memory responses, it offered a unique solution to the inefficacy of GUCY2C vaccines through recruitment of self-antigen-independent CD4(+) T-cell help. Incorporating CD4(+) T-cell epitopes from foreign antigens into vaccines against GUCY2C reconstituted CD4(+) T-cell help, revealing the latent functional capacity of GUCY2C-specific CD8(+) T- and B-cell pools, producing durable antitumor immunity without autoimmunity. Incorporating CD4(+) T-cell epitopes from foreign antigens into vaccines targeting self-antigens in melanoma (Trp2) and breast cancer (Her2) produced similar results, suggesting selective CD4(+) T-cell tolerance underlies ineffective vaccination against many cancer antigens. Thus, identification of self-antigens characterized by selective CD4(+) T-cell tolerance and abrogation of such tolerance through self-antigen-independent T-cell help is essential for future immunotherapeutics.

Role of cellular immunity in cow's milk allergy: pathogenesis, tolerance induction, and beyond

Food allergy is an aberrant immune-mediated reaction against harmless food substances, such as cow's milk proteins. Due to its very early introduction, cow's milk allergy is one of the earliest and most common food allergies. For this reason cow's milk allergy can be recognized as one of the first indications of an aberrant inflammatory response in early life. Classically, cow's milk allergy, as is true for most other allergies as well, is primarily associated with abnormal humoral immune responses, that is, elevation of specific immunoglobulin E levels. There is growing evidence indicating that cellular components of both innate and adaptive immunity play significant roles during the pathogenesis of cow's milk allergy. This is true for the initiation of the allergic phenotype (stimulation and skewing towards sensitization), development and outgrowth of the allergic disease. This review discusses findings pertaining to roles of cellular immunity in allergic inflammation, and tolerance induction against cow's milk proteins. In addition, a possible interaction between immune mechanisms underlying cow's milk allergy and other types of inflammation (infections and noncommunicable diseases) is discussed.

Molecules in medicine mini review: the αβ T cell receptor

As an integral part of the mammalian immune system, a distributed network of tissues, cells, and extracellular factors, T lymphocytes perform and control a multitude of activities that collectively contribute to the effective establishment, maintenance, and restoration of tissue and organismal integrity. Development and function of T cells is controlled by the T cell receptor (TCR), a heterodimeric cell surface protein uniquely expressed on T cells. During T cell development, the TCR undergoes extensive somatic diversification that generates a diverse T cell repertoire capable of recognizing an extraordinary range of protein and nonprotein antigens presented in the context of major histocompatibility complex molecules (MHC). In this review, we provide an introduction to the TCR, describing underlying principles that position this molecule as a central regulator of the adaptive immune system involved in responses ranging from tissue protection and preservation to pathology and autoimmunity.

Many faces of monogenic diabetes

Monogenic diabetes represents a heterogeneous group of disorders resulting from defects in single genes. Defects are categorized primarily into two groups: disruption of β-cell function or a reduction in the number of β-cells. A complex network of transcription factors control pancreas formation, and a dysfunction of regulators high in the hierarchy leads to pancreatic agenesis. Dysfunction among factors further downstream might cause organ hypoplasia, absence of islets of Langerhans or a reduction in the number of β-cells. Many transcription factors have pleiotropic effects, explaining the association of diabetes with other congenital malformations, including cerebellar agenesis and pituitary agenesis. Monogenic diabetes variants are classified conventionally according to age of onset, with neonatal diabetes occurring before the age of 6 months and maturity onset diabetes of the young (MODY) manifesting before the age of 25 years. Recently, certain familial genetic defects were shown to manifest as neonatal diabetes, MODY or even adult onset diabetes. Patients with neonatal diabetes require a thorough genetic work-up in any case, and because extensive phenotypic overlap exists between monogenic, type 2, and type 1 diabetes, genetic analysis will also help improve diagnosis in these cases. Next generation sequencing will facilitate rapid screening, leading to the discovery of digenic and oligogenic diabetes variants, and helping to improve our understanding of the genetics underlying other types of diabetes. An accurate diagnosis remains important, because it might lead to a change in the treatment of affected subjects and influence long-term complications.

A nationwide survey of Aicardi-Goutières syndrome patients identifies a strong association between dominant TREX1 mutations and chilblain lesions: Japanese cohort study

OBJECTIVES

Aicardi-Goutières syndrome (AGS) is a rare, genetically determined, early onset progressive encephalopathy associated with autoimmune manifestations. AGS is usually inherited in an autosomal recessive manner. The disease is rare, therefore the clinical manifestations and genotype-phenotype correlations, particularly with regard to autoimmune diseases, are still unclear. Here we performed a nationwide survey of AGS patients in Japan and analysed the genetic and clinical data.

METHODS

Patients were recruited via questionnaires sent to paediatric or adult neurologists in Japanese hospitals and institutions. Genetic analysis was performed and clinical data were collected.

RESULTS

Fourteen AGS patients were identified from 13 families; 10 harboured genetic mutations. Three patients harboured dominant-type TREX1 mutations. These included two de novo cases: one caused by a novel heterozygous p.His195Tyr mutation and the other by a novel somatic mosaicism resulting in a p.Asp200Asn mutation. Chilblain lesions were observed in all patients harbouring dominant-type TREX1 mutations. All three patients harbouring SAMHD1 mutations were diagnosed with autoimmune diseases, two with SLE and one with SS. The latter is the first reported case.

CONCLUSION

This study is the first to report a nationwide AGS survey, which identified more patients with sporadic AGS carrying de novo dominant-type TREX1 mutations than expected. There was a strong association between the dominant-type TREX1 mutations and chilblain lesions, and between SAMHD1 mutations and autoimmunity. These findings suggest that rheumatologists should pay attention to possible sporadic AGS cases presenting with neurological disorders and autoimmune manifestations.