Explore the vast range of titles available.

Multiple sclerosis (MS) is a debilitating autoimmune disease of the CNS, which is characterized by demyelination and axonal injury and frequently preceded by a demyelinating event called clinically isolated syndrome (CIS). Despite the importance of B cells and autoantibodies in MS pathology, their target specificities remain largely unknown. For an agnostic and comprehensive evaluation of autoantibodies in MS, we developed and employed what we believe to be a novel autoantigen discovery technology, the Antigenome Platform. This Platform is a high-throughput assay comprising large-fragment (approximately 100 amino acids) cDNA libraries, phage display, serum antibody screening technology, and robust bioinformatics analysis pipelines. For autoantibody discovery, we assayed serum samples from CIS patients who received either placebo or treatment who were enrolled in the REFLEX clinical trial, which assessed the effects of IFN-β-1a (Rebif) clinical and MRI activity in patients with CIS. Serum autoantibodies from patients with CIS were significantly and reproducibly enriched for known and previously unreported protein targets; 166 targets were selected by over 10% of patients' sera. Further, 10 autoantibody biomarkers associated with disease activity and 17 associated with patient response to IFN-β-1a therapy. These findings indicate widespread autoantibody production in MS and provide biomarkers for continued study and prediction of disease progression.

Cyclic GMP–AMP synthase (cGAS) is an innate immune sensor for cytosolic microbial DNA 1 . After binding DNA, cGAS synthesizes the messenger 2′3′-cyclic GMP–AMP (cGAMP) 2 – 4 , which triggers cell-autonomous defence and the production of type I interferons and pro-inflammatory cytokines via the activation of STING 5 . In addition to responding to cytosolic microbial DNA, cGAS also recognizes mislocalized cytosolic self-DNA and has been implicated in autoimmunity and sterile inflammation 6 , 7 . Specificity towards pathogen- or damage-associated DNA was thought to be caused by cytosolic confinement. However, recent findings place cGAS robustly in the nucleus 8 – 10 , where tight tethering of chromatin is important to prevent autoreactivity to self-DNA 8 . Here we show how cGAS is sequestered and inhibited by chromatin. We provide a cryo-electron microscopy structure of the cGAS catalytic domain bound to a nucleosome, which shows that cGAS does not interact with the nucleosomal DNA, but instead interacts with histone 2A–histone 2B, and is tightly anchored to the ‘acidic patch’. The interaction buries the cGAS DNA-binding site B, and blocks the formation of active cGAS dimers. The acidic patch robustly outcompetes agonistic DNA for binding to cGAS, which suggests that nucleosome sequestration can efficiently inhibit cGAS, even when accessible DNA is nearby, such as in actively transcribed genomic regions. Our results show how nuclear cGAS is sequestered by chromatin and provides a mechanism for preventing autoreactivity to nuclear self-DNA. Biochemical and structural analyses show how tethering of the nucleotidyltransferase cGAS to chromatin prevents autoimmune recognition of nuclear DNA.

Human leucocyte antigen B*27 (HLA-B*27) is strongly associated with inflammatory diseases of the spine and pelvis (for example, ankylosing spondylitis (AS)) and the eye (that is, acute anterior uveitis (AAU)) 1 . How HLA-B*27 facilitates disease remains unknown, but one possible mechanism could involve presentation of pathogenic peptides to CD8 + T cells. Here we isolated orphan T cell receptors (TCRs) expressing a disease-associated public β-chain variable region–complementary-determining region 3β (BV9–CDR3β) motif 2 – 4 from blood and synovial fluid T cells from individuals with AS and from the eye in individuals with AAU. These TCRs showed consistent α-chain variable region (AV21) chain pairing and were clonally expanded in the joint and eye. We used HLA-B*27:05 yeast display peptide libraries to identify shared self-peptides and microbial peptides that activated the AS- and AAU-derived TCRs. Structural analysis revealed that TCR cross-reactivity for peptide–MHC was rooted in a shared binding motif present in both self-antigens and microbial antigens that engages the BV9–CDR3β TCRs. These findings support the hypothesis that microbial antigens and self-antigens could play a pathogenic role in HLA-B*27-associated disease. A study shows that cross-reactivity of microbial antigens and self-antigens presented by HLA-B*27 may be important in the pathogenesis of diseases associated with HLA-B*27 and identifies the shared binding motif responsible.

The presence of antiendothelial cell antibodies (AECAs) has been documented in Takayasu arteritis (TAK), a chronic granulomatous vasculitis. Here, we identify cell-surface autoantigens using an expression cloning system. A cDNA library of endothelial cells is retrovirally transfected into a rat myeloma cell line from which AECA-positive clones are sorted with flow cytometry. Four distinct AECA-positive clones are isolated, and endothelial protein C receptor (EPCR) and scavenger receptor class B type 1 (SR-BI) are identified as endothelial autoantigens. Autoantibodies against EPCR and SR-BI are detected in 34.6% and 36.5% of cases, respectively, with minimal overlap (3.8%). Autoantibodies against EPCR are also detected in ulcerative colitis, the frequent comorbidity of TAK. In mechanistic studies, EPCR and SR-BI function as negative regulators of endothelial activation. EPCR has also an effect on human T cells and impair Th17 differentiation. Autoantibodies against EPCR and SR-BI block the functions of their targets, thereby promoting pro-inflammatory phenotype. Autoantibodies against endothelium have been recognized in Takayasu arteritis (TAK). Here the authors identify endothelial protein C receptor and scavenger receptor class B type 1 as major autoantigens in TAK, and find autoantibodies inhibit the negative regulation of endothelial activation.

Systemic autoimmune diseases are characterized by the failure of the immune system to differentiate self from non-self. These conditions are associated with significant morbidity and mortality, and they can affect many organs and systems, having significant clinical heterogeneity. Recent discoveries have highlighted that neutrophils, and in particular the neutrophil extracellular traps that they can release upon activation, can have central roles in the initiation and perpetuation of systemic autoimmune disorders and orchestrate complex inflammatory responses that lead to organ damage. Dysregulation of neutrophil cell death can lead to the modification of autoantigens and their presentation to the adaptive immune system. Furthermore, subsets of neutrophils that seem to be more prevalent in patients with systemic autoimmune disorders can promote vascular damage and increased oxidative stress. With the emergence of new technologies allowing for improved assessments of neutrophils, the complexity of neutrophil biology and its dysregulation is now starting to be understood. In this Review, we provide an overview of the roles of neutrophils in systemic autoimmune and autoinflammatory diseases and address putative therapeutic targets that may be explored based on this new knowledge.Neutrophils have a central role in the pathogenesis of systemic autoimmune and autoinflammatory diseases, particularly through neutrophil extracellular trap formation. Recent research suggests novel therapeutics targeting these structures that can improve patient outcomes.

CD1a-autoreactive T cells are common in human skin, but their natural antigens have remained unknown. De Jong and colleagues show that apolar oils that naturally accumulate in epidermis and sebum nest within CD1a and are activatory. T cells autoreactive to the antigen-presenting molecule CD1a are common in human blood and skin, but the search for natural autoantigens has been confounded by background T cell responses to CD1 proteins and self lipids. After capturing CD1a-lipid complexes, we gently eluted ligands while preserving non–ligand-bound CD1a for testing lipids from tissues. CD1a released hundreds of ligands of two types. Inhibitory ligands were ubiquitous membrane lipids with polar head groups, whereas stimulatory compounds were apolar oils. We identified squalene and wax esters, which naturally accumulate in epidermis and sebum, as autoantigens presented by CD1a. The activation of T cells by skin oils suggested that headless mini-antigens nest within CD1a and displace non-antigenic resident lipids with large head groups. Oily autoantigens naturally coat the surface of the skin; thus, this points to a previously unknown mechanism of barrier immunity.

The centromeric nucleosome Centromeres are epigenetically marked by the assembly of nucleosomes containing CENP-A, a centromere-specific histone H3 variant. Tachiwana et al . report the crystal structure of the human centromeric nucleosome bound to DNA. They find a canonical arrangement of an octamer of histone proteins with DNA wrapped in a left-handed superhelix. There is flexibility in the DNA regions at the entrance and exit of the nucleosome, and a loop in CENP-A may help to stabilize its incorporation into centromeric chromatin. As the first view of the CENP-A-containing nucleosome, the structure helps to clarify various models that have been debated in the literature. In eukaryotes, accurate chromosome segregation during mitosis and meiosis is coordinated by kinetochores, which are unique chromosomal sites for microtubule attachment 1 , 2 . Centromeres specify the kinetochore formation sites on individual chromosomes, and are epigenetically marked by the assembly of nucleosomes containing the centromere-specific histone H3 variant, CENP-A 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 . Although the underlying mechanism is unclear, centromere inheritance is probably dictated by the architecture of the centromeric nucleosome. Here we report the crystal structure of the human centromeric nucleosome containing CENP-A and its cognate α-satellite DNA derivative (147 base pairs). In the human CENP-A nucleosome, the DNA is wrapped around the histone octamer, consisting of two each of histones H2A, H2B, H4 and CENP-A, in a left-handed orientation. However, unlike the canonical H3 nucleosome, only the central 121 base pairs of the DNA are visible. The thirteen base pairs from both ends of the DNA are invisible in the crystal structure, and the αN helix of CENP-A is shorter than that of H3, which is known to be important for the orientation of the DNA ends in the canonical H3 nucleosome 13 . A structural comparison of the CENP-A and H3 nucleosomes revealed that CENP-A contains two extra amino acid residues (Arg 80 and Gly 81) in the loop 1 region, which is completely exposed to the solvent. Mutations of the CENP-A loop 1 residues reduced CENP-A retention at the centromeres in human cells. Therefore, the CENP-A loop 1 may function in stabilizing the centromeric chromatin containing CENP-A, possibly by providing a binding site for trans -acting factors. The structure provides the first atomic-resolution picture of the centromere-specific nucleosome.

Behcet's disease (BD) is a chronic systemic inflammatory vasculitis of unknown etiology characterized by recurrent episodes of oral aphthous ulcers, genital ulcers, skin lesions, ocular lesions, and other manifestations. Although the pathogenesis of BD is unclear, some studies have shown that immunological aberrations play an important role in the development and progression of BD. Infection-related trigger factors, including antigens and autoantigens, are believed to mediate the development of BD in patients with a genetic predisposition and subsequently activate the innate and adaptive immune systems, resulting in the production of numerous cytokines and chemokines to combat the infection-related factors. The study of the immunological mechanism of BD paves the way for the development of innovative therapies. Recently, novel biotherapy approaches, including interferon-α (IFN-α), tumor necrosis factor-α (TNF-α) antagonists, and other agents that target interleukins and their receptors, have shown promising results in the treatment of patients with refractory BD and have improved the prognosis of BD. In this review, we provide the current concepts of BD immunopathogenesis.

The striatin-interacting phosphatase and kinase (STRIPAK) complex is a large, multisubunit protein phosphatase 2A (PP2A) assembly that integrates diverse cellular signals in the Hippo pathway to regulate cell proliferation and survival. The architecture and assembly mechanism of this critical complex are poorly understood. Using cryo-EM, we determine the structure of the human STRIPAK core comprising PP2AA, PP2AC, STRN3, STRIP1, and MOB4 at 3.2-Å resolution. Unlike the canonical trimeric PP2A holoenzyme, STRIPAK contains four copies of STRN3 and one copy of each the PP2AA–C heterodimer, STRIP1, and MOB4. The STRN3 coiled-coil domains form an elongated homotetrameric scaffold that links the complex together. An inositol hexakisphosphate (IP 6 ) is identified as a structural cofactor of STRIP1. Mutations of key residues at subunit interfaces disrupt the integrity of STRIPAK, causing aberrant Hippo pathway activation. Thus, STRIPAK is established as a noncanonical PP2A complex with four copies of regulatory STRN3 for enhanced signal integration. A cryo-EM structure of the striatin-interacting phosphatase and kinase (STRIPAK) complex reveals the overall architecture of this large, multisubunit assembly that broadly regulates different signaling pathways.

Narcolepsy is a chronic sleep disorder caused by the loss of neurons that produce hypocretin. The close association with HLA-DQB1*06:02 , evidence for immune dysregulation and increased incidence upon influenza vaccination together suggest that this disorder has an autoimmune origin. However, there is little evidence of autoreactive lymphocytes in patients with narcolepsy. Here we used sensitive cellular screens and detected hypocretin-specific CD4 + T cells in all 19 patients that we tested; T cells specific for tribbles homologue 2—another self-antigen of hypocretin neurons—were found in 8 out of 13 patients. Autoreactive CD4 + T cells were polyclonal, targeted multiple epitopes, were restricted primarily by HLA-DR and did not cross-react with influenza antigens. Hypocretin-specific CD8 + T cells were also detected in the blood and cerebrospinal fluid of several patients with narcolepsy. Autoreactive clonotypes were serially detected in the blood of the same—and even of different—patients, but not in healthy control individuals. These findings solidify the autoimmune aetiology of narcolepsy and provide a basis for rapid diagnosis and treatment of this disease. The detection of hypocretin-specific autoreactive CD4 + and CD8 + T cells in patients with narcolepsy reveals the autoimmune aetiology of this disorder.