Search

Muscle cell death in polymyositis is induced by CD8 + cytotoxic T lymphocytes. We hypothesized that the injured muscle fibers release pro-inflammatory molecules, which would further accelerate CD8 + cytotoxic T lymphocytes-induced muscle injury, and inhibition of the cell death of muscle fibers could be a novel therapeutic strategy to suppress both muscle injury and inflammation in polymyositis. Here, we show that the pattern of cell death of muscle fibers in polymyositis is FAS ligand-dependent necroptosis, while that of satellite cells and myoblasts is perforin 1/granzyme B-dependent apoptosis, using human muscle biopsy specimens of polymyositis patients and models of polymyositis in vitro and in vivo. Inhibition of necroptosis suppresses not only CD8 + cytotoxic T lymphocytes-induced cell death of myotubes but also the release of inflammatory molecules including HMGB1. Treatment with a necroptosis inhibitor or anti-HMGB1 antibodies ameliorates myositis-induced muscle weakness as well as muscle cell death and inflammation in the muscles. Thus, targeting necroptosis in muscle cells is a promising strategy for treating polymyositis providing an alternative to current therapies directed at leukocytes., (© 2022. The Author(s).)

Interleukin-11 (IL-11) is a cytokine that has been strongly implicated in the pathogenesis of fibrotic diseases and solid malignancies. Elevated IL-11 expression is also associated with several non-malignant inflammatory diseases where its function remains less well-characterized. Here, we summarize current literature surrounding the contribution of IL-11 to the pathogenesis of autoimmune inflammatory diseases, including rheumatoid arthritis, multiple sclerosis, diabetes and systemic sclerosis, as well as other chronic inflammatory conditions such as periodontitis, asthma, chronic obstructive pulmonary disease, psoriasis and colitis., (Copyright © 2021 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Although hydroxychloroquine (HCQ) has long been used to treat autoimmune diseases, its mechanism of action remains poorly understood. In CD4 T-cells, we found that a clinically relevant concentration of HCQ inhibited the mitochondrial antioxidant system triggered by TCR crosslinking, leading to increased mitochondrial superoxide, impaired activation-induced autophagic flux, and reduced proliferation of CD4 T-cells. In antigen-presenting cells, HCQ also reduced constitutive activation of the endo-lysosomal protease legumain and toll-like receptor 9, thereby reducing cytokine production, but it had little apparent impact on constitutive antigen processing and peptide presentation. HCQ's effects did not require endo-lysosomal pH change, nor impaired autophagosome-lysosome fusion. We explored the clinical relevance of these findings in patients with celiac disease-a prototypic CD4 T-cell-mediated disease-and found that HCQ limits ex vivo antigen-specific T cell responses. We report a T-cell-intrinsic immunomodulatory effect from HCQ and suggest potential re-purposing of HCQ for celiac disease., Competing Interests: J.T-D. and M.Y.H. are inventors of patents pertaining to the use of gluten-derived T cell epitopes for use in CeD therapeutics. A.W.P. is a scientific advisor for Bioinformatics Solutions Inc. (providers of PEAKS X Pro software). I.P.W. is a scientific advisor for CSL Pty Ltd. The other authors declare no competing interests. All remaining authors declare no competing interests., (© 2021 The Author(s).)

Dendritic cells (DCs) and macrophages are at the forefront of immune responses, modifying their transcriptional programs in response to their tissue environment or immunological challenge. Posttranslational modifications of histones, such as histone H3 lysine-27 trimethylation (H3K27me3) by the Polycomb repressive complex 2 (PRC2), are tightly associated with epigenetic regulation of gene expression. To explore whether H3K27me3 is involved in either the establishment or function of the mononuclear phagocyte system, we selectively deleted core components of PRC2, either EZH2 or SUZ12, in CD11c-expressing myeloid cells. Unexpectedly, EZH2 deficiency neither prevented the deposition and maintenance of H3K27me3 in DCs nor hindered DC/macrophage homeostasis. In contrast, SUZ12 deficiency markedly impaired the capacity of DCs and macrophages to maintain H3K27me3. SUZ12 ablation induced a rapid loss of the alveolar macrophage and Langerhans cell networks under both steady state and inflammatory conditions because these cells could no longer proliferate to facilitate their self-renewal. Despite the reduced H3K27me3, DC development and function were unaffected by SUZ12 ablation, suggesting that PRC2-mediated gene repression was dispensable for DC homeostasis. Thus, the role of SUZ12 highlights the fundamentally different homeostatic mechanisms used by tissue-resident myeloid cells versus DCs.

Group 2 innate lymphoid cells (ILC2s) are essential to maintain tissue homeostasis. In cancer, ILC2s can harbor both pro-tumorigenic and anti-tumorigenic functions, but we know little about their underlying mechanisms or whether they could be clinically relevant or targeted to improve patient outcomes. Here, we found that high ILC2 infiltration in human melanoma was associated with a good clinical prognosis. ILC2s are critical producers of the cytokine granulocyte-macrophage colony-stimulating factor, which coordinates the recruitment and activation of eosinophils to enhance antitumor responses. Tumor-infiltrating ILC2s expressed programmed cell death protein-1, which limited their intratumoral accumulation, proliferation and antitumor effector functions. This inhibition could be overcome in vivo by combining interleukin-33-driven ILC2 activation with programmed cell death protein-1 blockade to significantly increase antitumor responses. Together, our results identified ILC2s as a critical immune cell type involved in melanoma immunity and revealed a potential synergistic approach to harness ILC2 function for antitumor immunotherapies.

Neutrophils help to clear pathogens and cellular debris, but can also cause collateral damage within inflamed tissues. Prolonged neutrophil residency within an inflammatory niche can exacerbate tissue pathology. Using both genetic and pharmacological approaches, we show that BCL-XL is required for the persistence of neutrophils within inflammatory sites in mice. We demonstrate that a selective BCL-XL inhibitor (A-1331852) has therapeutic potential by causing apoptosis in inflammatory human neutrophils ex vivo. Moreover, in murine models of acute and chronic inflammatory disease, it reduced inflammatory neutrophil numbers and ameliorated tissue pathology. In contrast, there was minimal effect on circulating neutrophils. Thus, we show a differential survival requirement in activated neutrophils for BCL-XL and reveal a new therapeutic approach to neutrophil-mediated diseases., (© 2021 by The American Society of Hematology.)

In rheumatoid arthritis (RA), extracellular vesicles (EVs) are associated with both the propagation and attenuation of joint inflammation and destruction. However, the specific EV content responsible for these processes is largely unknown. Investigations into identifying EV content are confounded by the challenges in obtaining high-quality EV preparations from synovial fluid. Implementing a size exclusion chromatography-based method of EV isolation, coupled with small RNA sequencing, we accurately characterised EV miRNAs in synovial fluid obtained from RA patients and investigated the differences between joints with high- and low-grade inflammation. Synovial fluid was obtained from the joints of 12 RA patients and, based on leukocyte counts, classified as either high ( n = 7)- or low ( n = 5)-grade inflammation. Using size exclusion chromatography, EVs were purified and small RNA was extracted and sequenced on a NextSeq 500. Sequencing reads were aligned to miRBase v21, and differences in miRNA profiles between RA patients with high- and low-grade joint inflammation were analysed. In total, 1972 distinct miRNAs were identified from RA synovial fluid EVs. miRNAs with less than five reads in fewer than five patients were filtered out, leaving 318 miRNAs for analysis. Analysis of the most abundant miRNAs suggested that they negatively regulate multiple genes relevant to inflammation, including signal transducer and activator of transcription 3 (STAT3), which lies downstream of IL-6 and has a pro-inflammatory role in RA. Synovial fluid from joints with high-grade inflammation contained 3.5-fold more EV miRNA per mL of synovial fluid ( p = 0.0017). Seventy-eight EV miRNAs were differentially expressed between RA joints with high- and low-grade inflammation, and pathway analysis revealed that their target genes were commonly involved a variety of processes, including cellular apoptosis, proliferation and migration. Of the 49 miRNAs that were elevated in joints with high-grade inflammation, pathway analysis revealed that genes involved in cytokine-mediated signalling pathways were significantly enriched targets. In contrast, genes associated with reactive oxygen species signalling were significantly enriched as targets of the 29 miRNAs elevated in joints with low-grade inflammation. Our study identified an abundance of EV miRNAs from the synovial fluid of RA patients with the potential to modulate inflammation. In doing so, we defined potential mechanisms by which synovial fluid EVs may contribute to RA pathophysiology.

Neutrophils are vital for the innate immune system's control of pathogens and neutrophil deficiency can render the host susceptible to life-threatening infections. Neutrophil responses must also be tightly regulated because excessive production, recruitment or activation of neutrophils can cause tissue damage in both acute and chronic inflammatory diseases. Granulocyte colony stimulating factor (G-CSF) is a key regulator of neutrophil biology, from production, differentiation, and release of neutrophil precursors in the bone marrow (BM) to modulating the function of mature neutrophils outside of the BM, particularly at sites of inflammation. G-CSF acts by binding to its cognate cell surface receptor on target cells, causing the activation of intracellular signalling pathways mediating the proliferation, differentiation, function, and survival of cells in the neutrophil lineage. Studies in humans and mice demonstrate that G-CSF contributes to protecting the host against infection, but conversely, it can play a deleterious role in inflammatory diseases. As such, neutrophils and the G-CSF pathway may provide novel therapeutic targets. This review will focus on understanding the role G-CSF plays in the balance between effective neutrophil mediated host defence versus neutrophil-mediated inflammation and tissue damage in various inflammatory and infectious diseases., (Copyright © 2021. Published by Elsevier Ltd.)

Natural killer (NK) cells are a specialised population of innate lymphoid cells (ILCs) that help control local immune responses. Through natural cytotoxicity, production of cytokines and chemokines, and migratory capacity, NK cells play a vital immunoregulatory role in the initiation and chronicity of inflammatory and autoimmune responses. Our understanding of their functional differences and contributions in disease settings is evolving owing to new genetic and functional murine proof-of-concept studies. Here, we summarise current understanding of NK cells in several classic autoimmune disorders, particularly in rheumatoid arthritis (RA), multiple sclerosis (MS), systemic lupus erythematosus (SLE) and type 1 diabetes mellitus (T1DM), but also less understood diseases such as idiopathic inflammatory myopathies (IIMs). A better understanding of how NK cells contribute to these autoimmune disorders may pave the way for NK cell-targeted therapeutics., Competing Interests: FSFG is a consultant for Biotheus Inc., (© 2021 The Authors. Clinical & Translational Immunology published by John Wiley & Sons Australia, Ltd on behalf of Australian and New Zealand Society for Immunology, Inc.)

Objective: To identify small noncoding RNA (sncRNA) serum biomarkers that predict response to triple disease-modifying antirheumatic drug (DMARD) therapy in patients with early rheumatoid arthritis (RA)., Methods: Early RA patients entered into a treat-to-target management algorithm, with triple DMARD therapy (methotrexate, sulfasalazine, hydroxychloroquine). Patients were assessed following 6 months of therapy and classified as European League Against Rheumatism responders or nonresponders. RNA was isolated from 42 archived serum samples, collected prior to commencement of triple DMARD therapy. Small RNA sequencing was performed and the reads mapped to annotations in a database of human sncRNA. Differential expression analysis was performed, comparing responders (n = 24) and nonresponders (n = 18)., Results: Pretreatment levels of 4 sncRNA were significantly increased in nonresponders: chr1. tRNA131-GlyCCC (4.1-fold, adjusted P = 0.01), chr2.tRNA13-AlaCGC (2.2-fold, adjusted P = 0.02), U2-L166 (6.6-fold, adjusted P = 0.02), and piR-35982 (2.4-fold, adjusted P = 0.03). 5S-L612 was the only sncRNA significantly increased in responders (3.3-fold; adjusted P = 0.01). Reads for chr1. tRNA131-GlyCCC and chr2.tRNA13-AlaCGC mapped to the 5' end of each tRNA gene and were truncated at the anticodon loop, consistent with these sncRNA having roles as 5' translation interfering tRNA halves (tiRNA)., Conclusion: Pretreatment levels of specific serum sncRNA might facilitate identification of patients more likely to respond to triple DMARD therapy.

Objectives: Rheumatoid arthritis (RA), an inflammatory joint disorder, independently increases the risk of cardiovascular disease (CVD). IL-1β contributes to both RA and CVD. We hypothesised that inhibiting IL-1 signalling with the IL-1R antagonist, anakinra, would dampen inflammation and promote resolution of atherosclerosis in arthritic mice., Methods: Low-density lipoprotein receptor (Ldlr)-deficient mice were fed a Western-type diet for 14 weeks to develop atherosclerotic plaques. Mice were then switched to a chow diet, promoting lesion regression, and randomised to a control group or into groups where arthritis was induced by passive transfer of K/BxN arthritogenic serum. The arthritic mice were further randomised to vehicle or anakinra., Results: Arthritis impaired atherosclerotic lesion regression when cholesterol was lowered. This was associated with a higher burden of plaque macrophages, likely due to monocytosis, driven by myelopoiesis in the bone marrow and spleen. Interestingly, delayed intervention with anakinra had no effect on arthritis in these mice. However, a significant improvement in atherosclerotic plaque remodelling to a more stable phenotype was observed. This was associated with fewer circulating monocytes, caused by a reduction in splenic extramedullary myelopoiesis., Conclusion: We show that inhibiting IL-1 signalling in arthritic mice with pre-existing atherosclerosis promotes lesion remodelling to a more stable phenotype, that is less likely to rupture and cause ischemic events such as myocardial infarction. This suggests that IL-1R antagonism may suppress CVD complications in patients with RA. Furthermore, inhibiting IL-1β signalling in other patients with inflammatory diseases that also predispose to CVD may also benefit from anti-IL-1 therapy., Competing Interests: The authors declare no conflict of interest., (© 2020 The Authors. Clinical & Translational Immunology published by John Wiley & Sons Australia, Ltd on behalf of Australian and New Zealand Society for Immunology, Inc.)

Objectives: Extracellular vesicles (EVs) from rheumatoid arthritis (RA) synovial fluid (SF) have been reported to stimulate the release of pro-inflammatory mediators from recipient cells. We recently developed a size exclusion chromatography (SEC)-based method for EV isolation capable of high-quality enrichments from human SF. Here, we employed this method to accurately characterise the SF EV proteome and investigate potential contributions to inflammatory pathways in RA., Methods: Using our SEC-based approach, SF EVs were purified from the joints of RA patients classified as having high-level ( n  = 7) or low-level inflammation ( n  = 5), and from osteoarthritis (OA) patients ( n  = 5). Protein profiles were characterised by mass spectrometry. Potential contributions of EV proteins to pathological pathways and differences in protein expression between disease groups were investigated., Results: Synovial fluid EVs were present at higher concentrations in RA joints with high-level inflammation ( P- value = 0.004) but were smaller in diameter ( P- value = 0.03) than in low-level inflammation. In total, 1058 SF EV proteins were identified by mass spectrometry analysis. Neutrophil and fibroblast markers were overrepresented in all disease groups. Numerous proteins with potential to modulate inflammatory and immunological processes were detected, including nine citrullinated peptides. Forty-five and 135 EV-associated proteins were significantly elevated in RA joints with high-level inflammation than in RA joints with low-level inflammation and OA joints, respectively. Gene ontology analysis revealed significant enrichment for proteins associated with 'neutrophil degranulation' within SF EVs from RA joints with high-level inflammation., Conclusion: Our results provide new information about SF EVs and insight into how EVs might contribute to the perpetuation of RA., Competing Interests: The authors declare no conflict of interest., (© 2020 The Authors. Clinical & Translational Immunology published by John Wiley & Sons Australia, Ltd on behalf of Australian and New Zealand Society for Immunology, Inc.)

The accumulation of cellular and environmental microparticles has been linked to many diseases associated with tissue inflammation. These particulate-driven diseases include joint, lung, kidney, cardiovascular, and neurodegenerative disorders. Recently a conserved proinflammatory inflammasome signaling pathway elicited by such microparticles has become apparent. Here, we review disease-promoting microparticles and the mechanisms by which they trigger activation of the inflammasome complexes responsible for generating bioactive interleukin-1β (IL-1β) and inducing cell death. We highlight how microparticle-induced inflammasome and cell death responses diverge from canonical inflammasome activators, and discuss the preclinical and clinical targeting of inflammasomes to treat microparticle-driven diseases., (Crown Copyright © 2020. Published by Elsevier Ltd. All rights reserved.)

Cell death is a vital process that occurs in billions of cells in the human body every day. This process helps maintain tissue homeostasis, supports recovery from acute injury, deals with infection and regulates immunity. Cell death can also provoke inflammatory responses, and lytic forms of cell death can incite inflammation. Loss of cell membrane integrity leads to the uncontrolled release of damage-associated molecular patterns (DAMPs), which are normally sequestered inside cells. Such DAMPs increase local inflammation and promote the production of cytokines and chemokines that modulate the innate immune response. Cell death can be both a consequence and a cause of inflammation, which can be difficult to distinguish in chronic diseases. Despite this caveat, excessive or poorly regulated cell death is increasingly recognized as a contributor to chronic inflammation in rheumatic disease and other inflammatory conditions. Drugs that inhibit cell death could, therefore, be used therapeutically for the treatment of these diseases, and programmes to develop such inhibitors are already underway. In this Review, we outline pathways for the major cell death programmes (apoptosis, necroptosis, pyroptosis and NETosis) and their potential roles in chronic inflammation. We also discuss current and developing therapies that target the cell death machinery.

The importance of tetraspanin proteins in regulating migration has been demonstrated in many diverse cellular systems. However, the function of the leukocyte-restricted tetraspanin CD53 remains obscure. We therefore hypothesized that CD53 plays a role in regulating leukocyte recruitment and tested this hypothesis by examining responses of CD53-deficient mice to a range of inflammatory stimuli. Deletion of CD53 significantly reduced neutrophil recruitment to the acutely inflamed peritoneal cavity. Intravital microscopy revealed that in response to several inflammatory and chemotactic stimuli, absence of CD53 had only minor effects on leukocyte rolling and adhesion in postcapillary venules. In contrast, Cd53 -/- mice showed a defect in leukocyte transmigration induced by TNF, CXCL1 and CCL2, and a reduced capacity for leukocyte retention on the endothelial surface under shear flow. Comparison of adhesion molecule expression in wild-type and Cd53 -/- neutrophils revealed no alteration in expression of β 2 integrins, whereas L-selectin was almost completely absent from Cd53 -/- neutrophils. In addition, Cd53 -/- neutrophils showed defects in activation-induced cytoskeletal remodeling and translocation to the cell periphery, responses necessary for efficient transendothelial migration, as well as increased α 3 integrin expression. These alterations were associated with effects on inflammation, so that in Cd53 -/- mice, the onset of neutrophil-dependent serum-induced arthritis was delayed. Together, these findings demonstrate a role for tetraspanin CD53 in promotion of neutrophil transendothelial migration and inflammation, associated with CD53-mediated regulation of L-selectin expression, attachment to the endothelial surface, integrin expression and trafficking, and cytoskeletal function., (Copyright © 2020 by The American Association of Immunologists, Inc.)

Despite increasing recognition of the importance of GM-CSF in autoimmune disease, it remains unclear how GM-CSF is regulated at sites of tissue inflammation. Using GM-CSF fate reporter mice, we show that synovial NK cells produce GM-CSF in autoantibody-mediated inflammatory arthritis. Synovial NK cells promote a neutrophilic inflammatory cell infiltrate, and persistent arthritis, via GM-CSF production, as deletion of NK cells, or specific ablation of GM-CSF production in NK cells, abrogated disease. Synovial NK cell production of GM-CSF is IL-18-dependent. Furthermore, we show that cytokine-inducible SH2-containing protein (CIS) is crucial in limiting GM-CSF signaling not only during inflammatory arthritis but also in experimental allergic encephalomyelitis (EAE), a murine model of multiple sclerosis. Thus, a cellular cascade of synovial macrophages, NK cells, and neutrophils mediates persistent joint inflammation via production of IL-18 and GM-CSF. Endogenous CIS provides a key brake on signaling through the GM-CSF receptor. These findings shed new light on GM-CSF biology in sterile tissue inflammation and identify several potential therapeutic targets., Competing Interests: Disclosures: Dr. Rautela is the co-founder and CEO of oNKo-innate Pty. Ltd. Dr. Masters reported personal fees from IFM Therapeutics, personal fees from Quench Bio, and grants from GlaxoSmithKline outside the submitted work. Dr. Babon reported a patent to inhibition of cytokine-induced sh2 protein in NK cells, licensed "Servier." Dr. Vivier reported personal fees from Innate Pharma during the conduct of the study; personal fees from Innate Pharma outside the submitted work; and is an employee of Innate Pharma. Dr. Huntington reported "other" from Servier during the conduct of the study; personal fees from ONKo-Innate outside the submitted work; has a patent to WO201700861A1 with royalties paid, Servier; and is the founder of oNKo-Innate Pty Ltd. Dr. Wicks reported, "I have argued that GM-CSF is an important therapeutic target in inflammatory diseases (see Wicks and Roberts, Nature Reviews Rheumatology 2016) and have provided advice around clinical translation to several companies interested in the area, namely Medimmune and Kiniksa. I have no relevant IP and these companies were not involved in the project described in our submission to JEM, nor did they provide funding. I don't believe there is any conflict of interest, but declare it because I have been an advocate for therapeutic antagonism of GM-CSF." No other disclosures were reported., (© 2020 Louis et al.)

Stimulator of Interferon Genes (STING) is a critical component of host innate immune defense but can contribute to chronic autoimmune or autoinflammatory disease. Once activated, the cyclic guanosine monophosphate (GMP)-adenosine monophosphate (AMP) (cGAMP) synthase (cGAS)-STING pathway induces both type I interferon (IFN) expression and nuclear factor-κB (NF-κB)-mediated cytokine production. Currently, these two signaling arms are thought to be mediated by a single upstream kinase, TANK-binding kinase 1 (TBK1). Here, using genetic and pharmacological approaches, we show that TBK1 alone is dispensable for STING-induced NF-κB responses in human and mouse immune cells, as well as in vivo. We further demonstrate that TBK1 acts redundantly with IκB kinase ε (IKKε) to drive NF-κB upon STING activation. Interestingly, we show that activation of IFN regulatory factor 3 (IRF3) is highly dependent on TBK1 kinase activity, whereas NF-κB is significantly less sensitive to TBK1/IKKε kinase inhibition. Our work redefines signaling events downstream of cGAS-STING. Our findings further suggest that cGAS-STING will need to be targeted directly to effectively ameliorate the inflammation underpinning disorders associated with STING hyperactivity., Competing Interests: Declaration of Interests S.L.M. receives funding from GlaxoSmithKline., (Copyright © 2020 The Author(s). Published by Elsevier Inc. All rights reserved.)

Objectives: Plasmacytoid dendritic cells (pDCs), through the production of type 1 interferons (IFNs) and other cytokines, are major contributors to systemic lupus erythematosus (SLE) pathogenesis. IL-3 promotes pDC survival, but its role in SLE is not well characterised. This study investigated serum IL-3 and IFN levels, and a whole blood 'IL-3 gene signature', in human SLE., Methods: Serum cytokine levels were measured by ELISA in n  = 42 SLE patients, and n  = 44 healthy donors. IL-3-regulated genes were determined by RNASeq of healthy donor whole blood cells (WBCs) stimulated in vitro with IL-3 for 6 or 24 h. Whole blood cell RNASeq analysis was undertaken in a separate cohort of n  = 31 SLE patients, and n  = 28 healthy donors., Results: Serum IL-3 levels correlated with IFNα ( r  = 0.612, 95% CI 0.455-0.733, P  < 0.001) and type III IFN ( r  = 0.585, 95% CI 0.406-0.720, P  < 0.0001). IL-3 stimulation of WBC in vitro altered 794 genes (-1 ≥ logFC ≥ 1, FDR < 0.05), of which 35 overlapped with genes differentially expressed between SLE and healthy donors. These 35 genes were expressed in 27/31 SLE donors, revealing the presence of an 'IL-3 gene signature'. There was strong correlation between the IL-3 signature and an IFN signature, as determined by hierarchical clustering of the 500 most variable genes in SLE donors ( r  = 0.939, 95% CI 0.898-0.964, P  < 0.0001)., Conclusion: A dual IL-3/IFN gene signature is a feature of SLE. An association between IL-3 and IFN raises the possibility that dual blockade of IL-3 and IFN may be especially useful for SLE patients with this dual cytokine gene signature., Competing Interests: SO, IPW, AH and EM have received research funding from CSL Limited. KM, MN, GV, EM, ADN and NJW are employees of CSL Limited, and KM, GV, EM, ADN and NJW hold stock in CSL Limited., (© 2019 The Authors. Clinical & Translational Immunology published by John Wiley & Sons Australia, Ltd on behalf of Australian and New Zealand Society for Immunology Inc.)

Objectives: To assess whether the neutrophil-lymphocyte ratio (NLR) and platelet-lymphocyte ratio (PLR) can predict those who subsequently require escalation of disease modifying therapy because of continued disease activity in rheumatoid arthritis (RA)., Methods: Patients with newly diagnosed RA were recruited from the Early Arthritis Clinic at the Royal Adelaide Hospital. All patients commenced "triple-therapy" with a standardised protocol of methotrexate, sulfasalazine and hydroxychloroquine, and were reviewed every three to six weeks. DMARD therapy was adjusted according to a pre-defined algorithm if not in low disease activity. The NLR, PLR and other markers of disease activity including ESR, CRP and DAS28 were collected, as well as current therapy. The primary outcome measure was failure of triple-therapy to maintain low-disease activity (DAS28<3.2) at 12 months., Results: Two-hundred and twenty-two patients met inclusion criteria. The mean age was 54.2 ± 15.4 years, with a mean disease duration of 22.3 ± 25.0 weeks. Forty-five (20%) patients had failed triple therapy by one year. The mean baseline NLR was significantly higher in those who failed triple therapy compared with those who did not (3.7 ± 2.8 vs. 2.9 ± 1.5; p = 0.02), however, the PLR was not significantly different. A baseline NLR>2.7 was an independent predictor of treatment failure (OR 2.65, CI 1.23-5.72, p = 0.01) whilst the PLR, ESR, CRP and DAS-28ESR were not., Conclusion: The NLR is significantly increased in those who subsequently fail triple-therapy for RA, and it outperformed conventional markers of disease activity. The NLR may offer an inexpensive, objective and reproducible prognostic marker in RA. Further studies are justified to confirm its potential role in guiding the management of RA., (Copyright © 2019 Elsevier Inc. All rights reserved.)

RNautophagy is a newly described type of selective autophagy whereby cellular RNAs are transported into lysosomes for degradation. This process involves the transmembrane protein SIDT2, which transports double-stranded RNA (dsRNA) across the endolysosomal membrane. We previously demonstrated that SIDT2 is a transcriptional target of p53, but its role in tumorigenesis, if any, is unclear. Unexpectedly, we show here that Sidt2 -/- mice with concurrent oncogenic Kras G12D activation develop significantly fewer tumors than littermate controls in a mouse model of lung adenocarcinoma. Consistent with this observation, loss of SIDT2 also leads to enhanced survival and delayed tumor development in an Apc min/+ mouse model of intestinal cancer. Within the intestine, Apc min/+ ;Sidt2 -/- mice display accumulation of dsRNA in association with increased phosphorylation of eIF2α and JNK as well as elevated rates of apoptosis. Taken together, our data demonstrate a role for SIDT2, and by extension RNautophagy, in promoting tumor development., (Copyright © 2019 The Author(s). Published by Elsevier Inc. All rights reserved.)

Objective: To investigate the impact of deleting Suppressor of Cytokine Signaling (SOCS)-3 (SOCS3) in chondrocytes during murine skeletal development., Method: Mice with a conditional Socs3 allele (Socs3 fl/fl ) were crossed with a transgenic mouse expressing Cre recombinase under the control of the type II collagen promoter (Col2a1) to generate Socs3 Δ/Δcol2 mice. Skeletal growth was analyzed over the lifespan of Socs3 Δ/Δcol2 mice and controls by detailed histomorphology. Bone size and cortical bone development was evaluated by micro-computed tomography (micro-CT). Growth plate (GP) zone width, chondrocyte proliferation and apoptosis were assessed by immunofluorescence staining for Ki67 and TUNEL. Fibroblast growth factor receptor-3 (FGFR3) signaling in the GP was assessed by immunohistochemistry, while the effect of SOCS3 overexpression on FGFR3-driven pMAPK signaling in HEK293T cells was evaluated by Western blot., Results: Socs3 Δ/Δcol2 mice of both sexes were consistently smaller compared to littermate controls throughout life. This phenotype was due to reduced long bone size, poor cortical bone development, reduced Ki67 + proliferative chondrocytes and decreased proliferative zone (PZ) width in the GP. Expression of pMAPK, but not pSTAT3, was increased in the GPs of Socs3 Δ/Δcol2 mice relative to littermate controls. Overexpression of FGFR3 in HEK293T cells increased Fibroblast Growth Factor 18 (FGF18)-dependent Mitogen-activated protein kinase (MAPK) phosphorylation, while concomitant expression of SOCS3 reduced FGFR3 expression and abrogated MAPK signaling., Conclusion: Our results suggest a potential role for SOCS3 in GP chondrocyte proliferation by regulating FGFR3-dependent MAPK signaling in response to FGF18., (Crown Copyright © 2019. Published by Elsevier Ltd. All rights reserved.)

The pyroptotic cell death effector gasdermin D (GSDMD) is required for murine models of hereditary inflammasome-driven, IL-1β-dependent, autoinflammatory disease, making it an attractive therapeutic target. However, the importance of GSDMD for more common conditions mediated by pathological IL-1β activation, such as gout, remain unclear. In this study, we address whether GSDMD and the recently described GSDMD inhibitor necrosulfonamide (NSA) contribute to monosodium urate (MSU) crystal-induced cell death, IL-1β release, and autoinflammation. We demonstrate that MSU crystals, the etiological agent of gout, rapidly activate GSDMD in murine macrophages. Despite this, the genetic deletion of GSDMD or the other lytic effector implicated in MSU crystal killing, mixed lineage kinase domain-like (MLKL), did not prevent MSU crystal-induced cell death. Consequently, GSDMD or MLKL loss did not hinder MSU crystal-mediated release of bioactive IL-1β. Consistent with in vitro findings, IL-1β induction and autoinflammation in MSU crystal-induced peritonitis was not reduced in GSDMD-deficient mice. Moreover, we show that the reported GSDMD inhibitor, NSA, blocks inflammasome priming and caspase-1 activation, thereby preventing pyroptosis independent of GSDMD targeting. The inhibition of cathepsins, widely implicated in particle-induced macrophage killing, also failed to prevent MSU crystal-mediated cell death. These findings 1) demonstrate that not all IL-1β-driven autoinflammatory conditions will benefit from the therapeutic targeting of GSDMD, 2) document a unique mechanism of MSU crystal-induced macrophage cell death not rescued by pan-cathepsin inhibition, and 3) show that NSA inhibits inflammasomes upstream of GSDMD to prevent pyroptotic cell death and IL-1β release., (Copyright © 2019 by The American Association of Immunologists, Inc.)

dsRNA is a common by-product of viral replication and acts as a potent trigger of antiviral immunity. SIDT1 and SIDT2 are closely related members of the SID-1 transmembrane family. SIDT2 functions as a dsRNA transporter and is required to traffic internalized dsRNA from endocytic compartments into the cytosol for innate immune activation, but the role of SIDT1 in dsRNA transport and in the innate immune response to viral infection is unclear. In this study, we show that Sidt1 expression is upregulated in response to dsRNA and type I IFN exposure and that SIDT1 interacts with SIDT2. Moreover, similar to SIDT2, SIDT1 localizes to the endolysosomal compartment, interacts with the long dsRNA analog poly(I:C), and, when overexpressed, enhances endosomal escape of poly(I:C) in vitro. To elucidate the role of SIDT1 in vivo, we generated SIDT1-deficient mice. Similar to Sidt2 -/- mice, SIDT1-deficient mice produced significantly less type I IFN following infection with HSV type 1. In contrast to Sidt2 -/- mice, however, SIDT1-deficient animals showed no impairment in survival postinfection with either HSV type 1 or encephalomyocarditis virus. Consistent with this, we observed that, unlike SIDT2, tissue expression of SIDT1 was relatively restricted, suggesting that, whereas SIDT1 can transport extracellular dsRNA into the cytoplasm following endocytosis in vitro, the transport activity of SIDT2 is likely to be functionally dominant in vivo., (Copyright © 2019 by The American Association of Immunologists, Inc.)

The adult heart contains macrophages derived from both embryonic and adult bone marrow (BM)-derived precursors. This population diversity prompted us to explore how distinct macrophage subsets localize within the heart, and their relative contributions in cardiac disease. In this study, using the reciprocal expression of Lyve-1 and Ccr2 to distinguish macrophages with distinct origins, we show that, in the steady state, both embryonic (Lyve pos ) and BM-derived (Ccr2 pos ) macrophages populate the major vessels of the heart in mice and humans. However, cardiac macrophage populations are markedly perturbed by inflammation. In a mouse model of Kawasaki disease, BM-derived macrophages preferentially increase during acute cardiac inflammation and selectively accumulate around major cardiac vessels. The accumulation of BM-derived macrophages coincides with the loss of their embryonic counterparts and is an initiating, essential step in the emergence of subsequent cardiac vasculitis in this experimental model. Finally, we demonstrate that the accumulation of Ccr2 pos macrophages (and the development of vasculitis) occurs in close proximity to a population of Ccr2 chemokine ligand-producing epicardial cells, suggesting that the epicardium may be involved in localizing inflammation to cardiac vessels. Collectively, our findings identify the perivascular accumulation of BM-derived macrophages as pivotal in the pathogenesis of cardiac vasculitis and provide evidence about the mechanisms governing their recruitment to the heart., (Copyright © 2019 by The American Association of Immunologists, Inc.)

Kawasaki disease (KD) is a leading cause of pediatric heart disease, characterized by the emergence of life-threatening coronary vasculitis. Identifying which cytokines drive KD has been a major research goal, and both TNF and IL-1 have been identified as potential candidates. Using a murine model of KD induced by the injection of the water-soluble component of Candida albicans , we therefore undertook a mechanistic study to determine how and when these two cytokines mediate cardiac inflammation. In this study, we show that TNF signaling is active in the acute phase of cardiac inflammation, which is characterized by a diffuse myocarditis that precedes the development of coronary vasculitis. Mechanistically, TNF is produced by the myeloid cells and triggers acute cardiac inflammation by stimulating both stromal and immune compartments of the heart. In contrast to this early involvement for TNF, IL-1 signaling is dispensable for the development of acute myocarditis. Critically, although mice deficient in IL-1 signaling have extensive acute inflammation following C. albicans water-soluble complex challenge, they do not develop coronary vasculitis. Thus, TNF and IL-1 appear to play temporally distinct roles in KD, with TNF being active in acute cardiac inflammation and IL-1 in the subsequent development of coronary vasculitis. These observations have important implications for understanding the progression of cardiac pathology in KD and the relative therapeutic use of targeting these cytokines., (Copyright © 2019 by The American Association of Immunologists, Inc.)

Objectives: NFIL3 is a key immunological transcription factor, with knockout mice studies identifying functional roles in multiple immune cell types. Despite the importance of NFIL3, little is known about its function in humans., Methods: Here, we characterised a kindred of two monozygotic twin girls with juvenile idiopathic arthritis at the genetic and immunological level, using whole exome sequencing, single cell sequencing and flow cytometry. Parallel studies were performed in a mouse model., Results: The patients inherited a novel p.M170I in NFIL3 from each of the parents. The mutant form of NFIL3 demonstrated reduced stability in vitro. The potential contribution of this mutation to arthritis susceptibility was demonstrated through a preclinical model, where Nfil3-deficient mice upregulated IL-1β production, with more severe arthritis symptoms on disease induction. Single cell sequencing of patient blood quantified the transcriptional dysfunctions present across the peripheral immune system, converging on IL-1β as a pivotal cytokine., Conclusions: NFIL3 mutation can sensitise for arthritis development, in mice and humans, and rewires the innate immune system for IL-1β over-production., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2019. Re-use permitted under CC BY. Published by BMJ.)

Objective: The production of class-switched high-affinity autoantibodies derived from organized germinal centers (GCs) is a hallmark of many autoimmune inflammatory diseases, including rheumatoid arthritis (RA). TANK-binding kinase 1 (TBK-1) is a serine/threonine kinase involved in the maturation of GC follicular helper T (Tfh) cells downstream of inducible costimulator signaling. We undertook this study to assess the therapeutic potential of TBK-1 inhibition using the small-molecule inhibitor WEHI-112 in antibody-dependent models of inflammatory arthritis., Methods: Using the models of collagen-induced arthritis (CIA), antigen-induced arthritis (AIA), and K/BxN serum-transfer-induced arthritis (STIA), we determined the effectiveness of WEHI-112 at inhibiting clinical and histologic features of arthritis in C57BL/6 and DBA/1 mice. We used immunohistochemistry to characterize GC populations during CIA development, and we used enzyme-linked immunosorbent assays to determine levels of Ig autoantibodies in WEHI-112-treated mice compared to vehicle-treated mice., Results: WEHI-112, a tool compound that is semiselective for TBK-1 but that also has activity against IKKε and JAK2, abolished TBK-1-dependent activation of interferon (IFN) regulatory factor 3 and inhibited type I IFN responses in vitro. In vivo, treatment with WEHI-112 selectively abrogated clinical and histologic features of established, antibody-dependent CIA, but had minimal effects on an antibody-independent model of AIA or on K/BxN STIA. In keeping with these findings, WEHI-112 reduced arthritogenic type II collagen-specific IgG1 and IgG2b antibody production. Furthermore, WEHI-112 altered the GC Tfh cell phenotype and GC B cell function in CIA., Conclusion: We report that TBK-1 inhibition using WEHI-112 abrogated antibody-dependent CIA. As WEHI-112 failed to inhibit non-antibody-driven joint inflammation, we conclude that the major effect of this compound was most likely the targeting of TBK-1-mediated mechanisms in the GC reaction. This approach may have therapeutic potential in RA and in other GC-associated autoantibody-driven inflammatory diseases., (© 2018, American College of Rheumatology.)

Background: Acute rheumatic fever (ARF) and rheumatic heart disease are autoimmune consequences of group A streptococcus infection and remain major causes of cardiovascular morbidity and mortality around the world. Improved treatment has been stymied by gaps in understanding key steps in the immunopathogenesis of ARF and rheumatic heart disease. This study aimed to identify (1) effector T cell cytokine(s) that might be dysregulated in the autoimmune response of patients with ARF by group A streptococcus, and (2) an immunomodulatory agent that suppresses this response and could be clinically translatable to high-risk patients with ARF., Methods: The immune response to group A streptococcus was analyzed in peripheral blood mononuclear cells from an Australian Aboriginal ARF cohort by a combination of multiplex cytokine array, flow cytometric analysis, and global gene expression analysis by RNA sequencing. The immunomodulatory drug hydroxychloroquine was tested for effects on this response., Results: We found a dysregulated interleukin-1β-granulocyte-macrophage colony-stimulating factor (GM-CSF) cytokine axis in ARF peripheral blood mononuclear cells exposed to group A streptococcus in vitro, whereby persistent interleukin-1β production is coupled to overproduction of GM-CSF and selective expansion of CXCR3 + CCR4 - CCR6 - CD4 T cells. CXCR3 + CCR4 - CCR6 - CD4 T cells are the major source of GM-CSF in human CD4 T cells and CXCL10, a CXCR3 ligand and potent T helper 1 chemoattractant, was elevated in sera from patients with ARF. GM-CSF has recently emerged as a key T cell-derived effector cytokine in numerous autoimmune diseases, including myocarditis, and the production of CXCL10 may explain selective trafficking of these cells to the heart. We provide evidence that interleukin-1β amplifies the expansion of GM-CSF-expressing CD4 T cells, which is effectively suppressed by hydroxychloroquine. RNA sequencing showed shifts in gene expression profiles and differentially expressed genes in peripheral blood mononuclear cells derived from patients at different clinical stages of ARF., Conclusions: Given the safety profile of hydroxychloroquine and its clinical pedigree in treating autoimmune diseases such as rheumatoid arthritis, where GM-CSF plays a pivotal role, we propose that hydroxychloroquine could be repurposed to reduce the risk of rheumatic heart disease after ARF.

Importance: Rheumatic immune-related adverse events (irAEs) occur in approximately 10-20% of anti-programmed death 1 (anti-PD1)-treated cancer patients. There are limited data on the natural history, optimal treatment and long-term oncological outcomes of patients with rheumatic irAEs., Objective: The objective of the study was to describe the spectrum and natural history of rheumatic irAEs and the potential impact of rheumatic irAEs and immunomodulators on anti-PD1 tumour efficacy., Methods: Cancer patients with pre-existing rheumatic disease before anti-PD1 therapy or de novo rheumatic irAEs on anti-PD1 therapy were retrospectively reviewed across three sites. Patient demographics, treatment history, anti-PD1 irAEs, and anti-PD1 responses were evaluated. Relationships between the development or pre-existence of rheumatic irAE, use of immunomodulatory agents and outcomes were evaluated., Results: This multicenter case series describes 36 cancer patients who had rheumatic disease before anti-PD1 therapy (n = 12) or developed de novo rheumatic irAEs (n = 24). Thirty-four of the 36 patients sustained rheumatic irAEs (median time to rheumatic irAE: 14.5 weeks), including 24 de novo (18 inflammatory arthritis, three myositis, two polymyalgia rheumatica, one fasciitis) and 10 flares in 12 patients with pre-existing rheumatic disease. Corticosteroids were used in 30 of 36 patients (median duration: 10 months), and disease-modifying antirheumatic drugs were used in 14 of 36 patients (median duration: 5.5 months). The objective response rate to anti-PD1 therapy was 69% (n = 25/36) overall and 81% (n = 21/26) in the melanoma subgroup., Conclusions: Rheumatic irAEs are often chronic and require prolonged immunomodulatory therapy. Prospective studies are required to define optimal management of rheumatic irAEs that maintain long-term anticancer outcomes., (Crown Copyright © 2018. Published by Elsevier Ltd. All rights reserved.)

Background: Monogenic autoinflammatory disorders are characterized by dysregulation of the innate immune system, for example by gain-of-function mutations in inflammasome-forming proteins, such as NOD-like receptor family CARD-containing 4 protein (NLRC4)., Objective: Here we investigate the mechanism by which a novel mutation in the leucine-rich repeat (LRR) domain of NLRC4 (c.G1965C, p.W655C) contributes to autoinflammatory disease., Methods: We studied 2 unrelated patients with early-onset macrophage activation syndrome harboring the same de novo mutation in NLRC4. In vitro inflammasome complex formation was quantified by using flow cytometric analysis of apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) specks. Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/Cas9 techniques and lentiviral transduction were used to generate THP-1 cells with either wild-type or mutant NLRC4 cDNA. Cell death and release of IL-1β/IL-18 were quantified by using flow cytometry and ELISA, respectively., Results: The p.W655C NLRC4 mutation caused increased ASC speck formation, caspase-1-dependent cell death, and IL-1β/IL-18 production. ASC contributed to p.W655C NLRC4-mediated cytokine release but not cell death. Mutation of p.W655 activated the NLRC4 inflammasome complex by engaging with 2 interfaces on the opposing LRR domain of the oligomer. One key set of residues (p.D1010, p.D1011, p.L1012, and p.I1015) participated in LRR-LRR oligomerization when triggered by mutant NLRC4 or type 3 secretion system effector (PrgI) stimulation of the NLRC4 inflammasome complex., Conclusion: This is the first report of a mutation in the LRR domain of NLRC4 causing autoinflammatory disease. c.G1965C/p.W655C NLRC4 increased inflammasome activation in vitro. Data generated from various NLRC4 mutations provides evidence that the LRR-LRR interface has an important and previously unrecognized role in oligomerization of the NLRC4 inflammasome complex., (Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.)

Objectives: To report on the design, implementation and evaluation of the safety and effectiveness of the Back pain Assessment Clinic (BAC) model., Design: BAC is a new, community-based specialist service for assessing and managing neck and low back pain (LBP). The BAC pilot was supported by a Victorian Department of Health and Human Services grant and was evaluated using the Victorian Innovation Reform Impact Assessment Framework (VIRIAF). Data were obtained by auditing BAC activity (22 July 2014 to 30 June 2015) and conducting surveys and interviews of patients, stakeholders and referrers., Setting: Tertiary and primary care., Participants: Adult patients with neck and LBP referred for outpatient surgical consultation., Main Outcome Measures: VIRIAF outcomes: (1) access to care; (2) appropriate and safe care; (3) workforce optimisation and integration; and (4) efficiency and sustainability., Results: A total of 522 patients were seen during the pilot. Most were referred to hospital services by general practitioners (87%) for LBP (63%) and neck pain (24%). All patients were seen within 10 weeks of referral and commenced community-based allied health intervention within 2-4 weeks of assessment in BAC. Of patients seen, 34% had medications adjusted, 57% were referred for physiotherapy, 3.2% to pain services, 1.1% to rheumatology and 1.8% for surgical review. Less MRI scans were ordered in BAC (6.4%) compared with traditional spinal surgical clinics (89.8%), which translated to a cost-saving of $52 560 over 12 months. Patient and staff satisfaction was high. There have been no patient complaints or adverse incidents., Conclusion: Evaluation of the BAC pilot suggests it is a potentially safe and cost-saving alternative model of care. Results of the BAC pilot merit further evaluation to determine the potential cost-effectiveness, longer term and broader societal impact of implementing BAC more widely., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2018. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

As a complex biological fluid, human synovial fluid (SF) presents challenges for extracellular vesicle (EV) enrichment using standard methods. In this study of human SF, a size exclusion chromatography (SEC)-based method of EV enrichment is shown to deplete contaminants that remain after standard ultracentrifugation-based enrichment methods. Specifically, considerable levels of serum albumin, the high-density lipoprotein marker, apolipoprotein A-I, fibronectin and other extracellular proteins and debris are present in EVs prepared by differential ultracentrifugation. While the addition of a sucrose density gradient purification step improved purification quality, some contamination remained. In contrast, using a SEC-based approach, SF EVs were efficiently separated from serum albumin, apolipoprotein A-I and additional contaminating proteins that co-purified with high-speed centrifugation. Finally, using high-resolution mass spectrometry analysis, we found that residual contaminants which remain after SEC, such as fibronectin and other extracellular proteins, can be successfully depleted by proteinase K. Taken together, our results highlight the limitations of ultracentrifugation-based methods of EV isolation from complex biological fluids and suggest that SEC can be used to obtain higher purity EV samples. In this way, SEC-based methods are likely to be useful for identifying EV-enriched components and improving understanding of EV function in disease.

Aim: Rheumatoid arthritis (RA) is associated with an approximately two-fold elevated risk of cardiovascular (CV)-related mortality. Patients with RA present with systemic inflammation including raised circulating myeloid cells, but fail to display traditional CV risk-factors, particularly dyslipidaemia. We aimed to explore if increased circulating myeloid cells is associated with impaired atherosclerotic lesion regression or altered progression in RA., Methods and Results: Using flow cytometry, we noted prominent monocytosis, neutrophilia, and thrombocytosis in two mouse models of RA. This was due to enhanced proliferation of the haematopoietic stem and progenitor cells (HSPCs) in the bone marrow and the spleen. HSPCs expansion was associated with an increase in the cholesterol content, due to a down-regulation of cholesterol efflux genes, Apoe, Abca1, and Abcg1. The HSPCs also had enhanced expression of key myeloid promoting growth factor receptors. Systemic inflammation was found to cause defective cellular cholesterol metabolism. Increased myeloid cells in mice with RA were associated with a significant impairment in lesion regression, even though cholesterol levels were equivalent to non-arthritic mice. Lesions from arthritic mice exhibited a less stable phenotype as demonstrated by increased immune cell infiltration, lipid accumulation, and decreased collagen formation. In a progression model, we noted monocytosis, enhanced monocytes recruitment to lesions, and increased plaque macrophages. This was reversed with administration of reconstituted high-density lipoprotein (rHDL). Furthermore, RA patients have expanded CD16+ monocyte subsets and a down-regulation of ABCA1 and ABCG1., Conclusion: Rheumatoid arthritis impairs atherosclerotic regression and alters progression, which is associated with an expansion of myeloid cells and disturbed cellular cholesterol handling, independent of plasma cholesterol levels. Infusion of rHDL prevented enhanced myelopoiesis and monocyte entry into lesions. Targeting cellular cholesterol defects in people with RA, even if plasma cholesterol is within the normal range, may limit vascular disease.

Neutrophil extracellular traps (NETs) and the cell death associated with it (NETosis) have been implicated in numerous diseases. Mechanistic studies of NETosis have typically relied on nonphysiological stimuli, such as PMA. The human disease of gout is caused by monosodium urate (MSU) crystals. We observed that DNA consistent with NETs is present in fluid from acutely inflamed joints of gout patients. NETs also coat the crystals found in uninflamed tophi of chronic gout patients. We developed a quantitative, live cell imaging assay, which measures the key features of NETosis, namely, cell death and chromatin decondensation. We show that MSU and other physiologically relevant crystals induce NETosis through a molecular pathway that is distinct from PMA and Candida hyphae. Crystals interact with lysosomes to induce NADPH oxidase-independent cell death, with postmortem chromatin decondensation mediated by neutrophil elastase. The resulting MSU-induced NETs are enriched for actin and are resistant to serum and DNase degradation. These findings demonstrate a distinct physiological NETosis pathway in response to MSU crystals, which coats MSU crystals in DNA that persists in tissues as gouty tophi., (Copyright © 2018 by The American Association of Immunologists, Inc.)

Objective: Pyrin-Associated Autoinflammation with Neutrophilic Dermatosis (PAAND) is a recently described monogenic autoinflammatory disease. The causal p.S242R MEFV mutation disrupts a binding motif of the regulatory 14-3-3 proteins within pyrin. Here, we investigate a family with clinical features consistent with PAAND in whom the novel p.E244K MEFV mutation, located in the +2 site of the 14-3-3 binding motif in pyrin, has been found., Methods: Multiplex cytokine analyses were performed on p.E244K patient and control serum. Peripheral blood mononuclear cells were stimulated ex vivo with lipopolysaccharide (LPS). In vitro, inflammasome complex formation was evaluated by flow cytometry of Apoptosis-associated Speck-like protein containing a Caspase recruitment domain (ASC) specks. Interleukin-1β (IL-1β) and IL-18 production was quantified by ELISA. The ability of the p.E244K pyrin mutation to interact with 14-3-3 was assessed by immunoprecipitation., Results: PAAND p.E244K patient serum displayed a different cytokine profile compared with patients with Familial Mediterranean Fever (FMF). In overexpression models, p.E244K pyrin was associated with decreased 14-3-3 binding and increased ASC speck formation. THP-1 monocytes expressing PAAND pyrin mutations demonstrated spontaneous caspase-1-dependent IL-1β and IL-18 secretion, as well as cell death, which were significantly greater than those of wild-type and the FMF-associated mutation p.M694V., Conclusion: In PAAND, disruption of the +2 position of a 14-3-3 binding motif in pyrin results in its constitutive activation, with spontaneous production of IL-1β and IL-18, associated with inflammatory cell death. The altered serum cytokine profile may explain the different clinical features exhibited by PAAND patients compared with those with FMF., Competing Interests: Competing interests: None declared., (© Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2017. All rights reserved. No commercial use is permitted unless otherwise expressly granted.)

Double-stranded RNA (dsRNA) is a common by-product of viral infections and acts as a potent trigger of antiviral immunity. In the nematode C. elegans, sid-1 encodes a dsRNA transporter that is highly conserved throughout animal evolution, but the physiological role of SID-1 and its orthologs remains unclear. Here, we show that the mammalian SID-1 ortholog, SIDT2, is required to transport internalized extracellular dsRNA from endocytic compartments into the cytoplasm for immune activation. Sidt2-deficient mice exposed to extracellular dsRNA, encephalomyocarditis virus (EMCV), and herpes simplex virus 1 (HSV-1) show impaired production of antiviral cytokines and-in the case of EMCV and HSV-1-reduced survival. Thus, SIDT2 has retained the dsRNA transport activity of its C. elegans ortholog, and this transport is important for antiviral immunity., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Introduction and Objectives: Pneumocystis jirovecii pneumonia (PJP) is an opportunistic fungal infection that affects the immunocompromised. Patients with systemic autoimmune rheumatic disease are increasingly recognised as an at-risk clinical population with a high mortality. This case-control study examined differences in the characteristics and peripheral blood parameters between patients with systemic autoimmune rheumatic disease who developed PJP and gender, age and disease-matched controls., Methods: Historical data collected between 2002 and 2013 at the Royal Melbourne Hospital, Australia were reviewed. Cases were defined by having a systemic autoimmune rheumatic disease and a diagnosis of PJP (either a positive toluidine blue O stain or P. jirovecii PCR, with a concurrent respiratory illness that was clinically consistent with PJP). Controls were matched for age, gender and disease in a 4:1 ratio. Peripheral blood results were retrieved from an in-house pathology database. Clinical information including glucocorticoid exposure, PJP prophylaxis, comorbidities and month of admission were retrieved from medical notes., Results: After adjustment for corticosteroid exposure and C-reactive protein, lymphocyte count on admission (0.4 vs. 1.3; p = 0.04) and at nadir (0.2 vs. 0.8 × 10 9 /L; p = 0.05) was significantly lower in cases than in controls. Cases (n = 11) were more frequently Caucasian rather than non-Caucasian (81.8% vs. 65.9%; p = 0.04). In addition, cases more commonly presented in autumn (March to May) than in other seasons (OR = 7.3; 95% CI: 1.4-38.7; p = 0.02)., Conclusion: These data demonstrate that patients with systemic autoimmune rheumatic disease who develop PJP have significantly greater lymphopenia than age, gender and disease-matched controls, independent of corticosteroid exposure, as well as a potential ethnicity and seasonal predilection to PJP. This may help to inform prophylactic guidelines for PJP in these patients., (Copyright © 2017 Elsevier Inc. All rights reserved.)

G-CSF is a hemopoietic growth factor that has a role in steady state granulopoiesis, as well as in mature neutrophil activation and function. G-CSF- and G-CSF receptor-deficient mice are profoundly protected in several models of rheumatoid arthritis, and Ab blockade of G-CSF also protects against disease. To further investigate the actions of blocking G-CSF/G-CSF receptor signaling in inflammatory disease, and as a prelude to human studies of the same approach, we developed a neutralizing mAb to the murine G-CSF receptor, which potently antagonizes binding of murine G-CSF and thereby inhibits STAT3 phosphorylation and G-CSF receptor signaling. Anti-G-CSF receptor rapidly halted the progression of established disease in collagen Ab-induced arthritis in mice. Neutrophil accumulation in joints was inhibited, without rendering animals neutropenic, suggesting an effect of G-CSF receptor blockade on neutrophil homing to inflammatory sites. Consistent with this, neutrophils in the blood and arthritic joints of anti-G-CSF receptor-treated mice showed alterations in cell adhesion receptors, with reduced CXCR2 and increased CD62L expression. Furthermore, blocking neutrophil trafficking with anti-G-CSF receptor suppressed local production of proinflammatory cytokines (IL-1β, IL-6) and chemokines (KC, MCP-1) known to drive tissue damage. Differential gene expression analysis of joint neutrophils showed a switch away from an inflammatory phenotype following anti-G-CSF receptor therapy in collagen Ab-induced arthritis. Importantly, G-CSF receptor blockade did not adversely affect viral clearance during influenza infection in mice. To our knowledge, we describe for the first time the effect of G-CSF receptor blockade in a therapeutic model of inflammatory joint disease and provide support for pursuing this therapeutic approach in treating neutrophil-associated inflammatory diseases., (Copyright © 2016 by The American Association of Immunologists, Inc.)

Kawasaki disease (KD) is the leading cause of pediatric heart disease in developed countries. KD patients develop cardiac inflammation, characterized by an early infiltrate of neutrophils and monocytes that precipitates coronary arteritis. Although the early inflammatory processes are linked to cardiac pathology, the factors that regulate cardiac inflammation and immune cell recruitment to the heart remain obscure. In this study, using a mouse model of KD (induced by a cell wall Candida albicans water-soluble fraction [CAWS]), we identify an essential role for granulocyte/macrophage colony-stimulating factor (GM-CSF) in orchestrating these events. GM-CSF is rapidly produced by cardiac fibroblasts after CAWS challenge, precipitating cardiac inflammation. Mechanistically, GM-CSF acts upon the local macrophage compartment, driving the expression of inflammatory cytokines and chemokines, whereas therapeutically, GM-CSF blockade markedly reduces cardiac disease. Our findings describe a novel role for GM-CSF as an essential initiating cytokine in cardiac inflammation and implicate GM-CSF as a potential target for therapeutic intervention in KD., (© 2016 Stock et al.)

To date, the major target of biologic therapeutics in systemic lupus erythematosus (SLE) has been the B cell, which produces pathogenic autoantibodies. Recently, targeting type I IFN, which is elaborated by plasmacytoid dendritic cells (pDCs) in response to endosomal TLR7 and TLR9 stimulation by SLE immune complexes, has shown promising results. pDCs express high levels of the IL-3Rα chain (CD123), suggesting an alternative potential targeting strategy. We have developed an anti-CD123 monoclonal antibody, CSL362, and show here that it affects key cell types and cytokines that contribute to SLE. CSL362 potently depletes pDCs via antibody-dependent cell-mediated cytotoxicity, markedly reducing TLR7, TLR9, and SLE serum-induced IFN-α production and IFN-α-upregulated gene expression. The antibody also inhibits TLR7- and TLR9-induced plasmablast expansion by reducing IFN-α and IL-6 production. These effects are more pronounced than with IFN-α blockade alone, possibly because pDC depletion reduces production of other IFN subtypes, such as type III, as well as non-IFN proinflammatory cytokines, such as IL-6. In addition, CSL362 depletes basophils and inhibits IL-3 signaling. These effects were confirmed in cells derived from a heterogeneous population of SLE donors, various IFN-dependent autoimmune diseases, and healthy controls. We also demonstrate in vivo activity of CSL362 following its s.c. administration to cynomolgus monkeys. This spectrum of effects provides a preclinical rationale for the therapeutic evaluation of CSL362 in SLE.

Objective: To investigate the effect of suppressing inflammation on retinal microvascular health in patients with RA., Methods: Two groups of patients with RA were recruited and studied concurrently. Group A included patients with moderate to high disease activity [28-joint DAS with CRP (DAS28-CRP) >3.2] requiring treatment escalation, while group B had stable low disease activity (DAS28-CRP ≤3.2) not requiring treatment escalation. Retinal photography was performed at baseline and weeks 6 and 24 in group A and at baseline and week 12 in group B., Results: Group A included 26 patients with a mean age of 50.7 years (s.d. 3.5) and a mean disease duration of 7.1 years (s.d. 8.0). Disease activity significantly improved during follow-up and was accompanied by a significant reduction in retinal venular calibre at week 6 [mean difference (MD) -7.9 μm (95% CI -13.3, -2.5)] and at week 24 [MD -6.8 μm (95% CI -12.2, -1.4)]. No significant change in retinal arteriolar calibre was identified at week 6 [MD -0.6 μm (95% CI -4.5, 3.28)] or week 24 [MD 0.7 μm (95% CI -3.1, 4.5)]. Group B included 27 patients with a mean age of 54.6 years (s.d. 1.8) and a mean disease duration of 14.5 years (s.d. 10.9). Disease activity and therapy remained unchanged during follow-up and no significant changes in retinal venular [MD 1.81 μm (95% CI -2.32, 5.95)] or arteriolar [MD 0.54 μm (95% CI -2.77, 3.86)] calibre were observed., Conclusion: We demonstrated that suppression of inflammation in RA is associated with a reduction of retinal venular calibre, suggesting that therapies targeting inflammation could improve vascular health in RA., (© The Author 2015. Published by Oxford University Press on behalf of the British Society for Rheumatology. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

Granulocyte-macrophage colony stimulating factor (GM-CSF) is a growth factor first identified as an inducer of differentiation and proliferation of granulocytes and macrophages derived from haematopoietic progenitor cells. Later studies have shown that GM-CSF is involved in a wide range of biological processes in both innate and adaptive immunity, with its production being tightly linked to the response to danger signals. Given that the functions of GM-CSF span multiple tissues and biological processes, this cytokine has shown potential as a new and important therapeutic target in several autoimmune and inflammatory disorders - particularly in rheumatoid arthritis. Indeed, GM-CSF was one of the first cytokines detected in human synovial fluid from inflamed joints. Therapies that target GM-CSF or its receptor have been tested in preclinical studies with promising results, further supporting the potential of targeting the GM-CSF pathway. In this Review, we discuss our expanding view of the biology of GM-CSF, outline what has been learnt about GM-CSF from studies of animal models and human diseases, and summarize the results of early phase clinical trials evaluating GM-CSF antagonism in inflammatory disorders.

Granulocyte colony-stimulating factor (G-CSF) is a regulator of neutrophil production, function, and survival. Herein, we investigated the role of G-CSF in a murine model of human uveitis-experimental autoimmune uveoretinitis. Experimental autoimmune uveoretinitis was dramatically reduced in G-CSF-deficient mice and in anti-G-CSF monoclonal antibody-treated, wild-type (WT) mice. Flow cytometric analysis of the ocular infiltrate in WT mice with experimental autoimmune uveoretinitis showed a mixed population, comprising neutrophils, macrophages, and T cells. The eyes of G-CSF-deficient and anti-G-CSF monoclonal antibody-treated WT mice had minimal neutrophil infiltrate, but no change in other myeloid-derived inflammatory cells. Antigen-specific T-cell responses were maintained, but the differentiation of pathogenic type 17 helper T cells in experimental autoimmune uveoretinitis was reduced with G-CSF deficiency. We show that G-CSF controls the ocular neutrophil infiltrate by modulating the expression of C-X-C chemokine receptors 2 and 4 on peripheral blood neutrophils, as well as actin polymerization and migration. These data reveal an integral role for G-CSF-driven neutrophil responses in ocular autoimmunity, operating within and outside of the bone marrow, and also identify G-CSF as a potential therapeutic target in the treatment of human uveoretinitis., (Copyright © 2016 American Society for Investigative Pathology. Published by Elsevier Inc. All rights reserved.)

Objective: To describe gene expression in murine chondrocytes stimulated with IL-6 family cytokines and the impact of deleting Suppressor of Cytokine Signaling-3 (SOCS-3) in this cell type., Method: Primary chondrocytes were isolated from wild type and SOCS-3-deficient (Socs3(Δ/Δcol2)) mice and stimulated with oncostatin M (OSM), IL-6 plus the soluble IL-6 receptor (IL-6/sIL-6R), IL-11 or leukemia inhibitory factor (LIF) for 4 h. Total RNA was extracted and gene expression was evaluated by microarray analysis. Validation of the microarray results was performed using Taqman probes on RNA derived from chondrocytes stimulated for 1, 2, 4 or 8 h. Gene ontology was characterized using DAVID (database for annotation, visualization and integrated discovery)., Results: Multiple genes, including Bcl3, Junb, Tgm1, Angptl4 and Lrg1, were upregulated in chondrocytes stimulated with each gp130 cytokine. The gene transcription profile in response to OSM stimulation was pro-inflammatory and was highly correlated to IL-6/sIL-6R, rather than IL-11 or LIF. In the absence of SOCS-3, OSM and IL-6/sIL-6R stimulation induced an interferon (IFN)-like gene signature, including expression of IL-31ra and S100a9., Conclusion: While each gp130 cytokine induced a transcriptional response in chondrocytes, OSM- and IL-6/sIL-6R were the most potent members of this cytokine family. SOCS-3 plays an important regulatory role in this cell type, as it does in hematopoietic cells. Our results provide new insights into a hierarchy of gp130-induced transcriptional responses in chondrocytes that is normally restrained by SOCS-3 and suggest therapeutic inhibition of OSM may have benefit over and above antagonism of IL-6 during inflammatory arthritis., (Copyright © 2015 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.)

Objective: Previous work has suggested that the granulocyte macrophage colony stimulating factor (GM-CSF)-GM-CSF receptor α axis (GM-CSFRα) may provide a new therapeutic target for the treatment of rheumatoid arthritis (RA). Therefore, we investigated the cellular expression of GM-CSFRα in RA synovial tissue and investigated the effects of anti-GM-CSFRα antibody treatment in vitro and in vivo in a preclinical model of RA., Methods: We compared GM-CSFRα expression on macrophages positive for CD68 or CD163 on synovial biopsy samples from patients with RA or psoriatic arthritis (PsA) to disease controls. In addition, we studied the effects of CAM-3003, an anti-GM-CSFR antibody in a collagen induced arthritis model of RA in DBA/1 mice. The pharmacokinetic profile of CAM-3003 was studied in naïve CD1(ICR) mice (see online supplement) and used to interpret the results of the pharmacodynamic studies in BALB/c mice., Results: GM-CSFRα was expressed by CD68 positive and CD163 positive macrophages in the synovium, and there was a significant increase in GM-CSFRα positive cells in patients in patients with RA as well as patients with PsA compared with patients with osteoarthritis and healthy controls. In the collagen induced arthritis model there was a dose dependent reduction of clinical arthritis scores and the number of F4/80 positive macrophages in the inflamed synovium after CAM-3003 treatment. In BALB/c mice CAM-3003 inhibited recombinant GM-CSF mediated margination of peripheral blood monocytes and neutrophils., Conclusions: The findings support the ongoing development of therapies aimed at interfering with GM-CSF or its receptor in various forms of arthritis, such as RA and PsA., (Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.)

There is a pressing need to reduce the high global disease burden of rheumatic heart disease (RHD) and its harbinger, acute rheumatic fever (ARF). ARF is a classical example of an autoimmune syndrome and is of particular immunological interest because it follows a known antecedent infection with group A streptococcus (GAS). However, the poorly understood immunopathology of these post-infectious diseases means that, compared to much progress in other immune-mediated diseases, we still lack useful biomarkers, new therapies or an effective vaccine in ARF and RHD. Here, we summarise recent literature on the complex interaction between GAS and the human host that culminates in ARF and the subsequent development of RHD. We contrast ARF with other post-infectious streptococcal immune syndromes - post-streptococcal glomerulonephritis (PSGN) and the still controversial paediatric autoimmune neuropsychiatric disorders associated with streptococcal infections (PANDAS), in order to highlight the potential significance of variations in the host immune response to GAS. We discuss a model for the pathogenesis of ARF and RHD in terms of current immunological concepts and the potential for application of in depth "omics" technologies to these ancient scourges., (Copyright © 2015 Elsevier B.V. All rights reserved.)