Pathogenesis Of sJIA Research Articles

Serum interleukin-18 levels can improve the diagnostic performance of the PRINTO and ILAR criteria for systemic juvenile idiopathic arthritis

ObjectiveRecently, the Pediatric Rheumatology International Trials Organization (PRINTO) has proposed revisions to the current International League of Associations for Rheumatology (ILAR) criteria for systemic juvenile idiopathic arthritis (s-JIA). Interleukin (IL)-18 overproduction plays a significant role in the pathogenesis of s-JIA. This study aimed to evaluate the performance of the PRINTO criteria compared with the ILAR criteria and determine whether serum IL-18 levels improve their diagnostic performances. MethodsOverall, 90 patients with s-JIA and 27 patients with other febrile disease controls presenting with a prolonged fever of > 14 days and arthritis and/or erythematous rash were enrolled. The ILAR and PRINTO classification criteria were applied to all patients and examined with expert diagnoses. Enzyme-linked immunosorbent assay was used for measuring serum IL-18 levels. ResultsThe PRINTO criteria had higher sensitivity but lower specificity than the ILAR criteria (sensitivity: PRINTO 0.856, ILAR 0.533; specificity: PRINTO 0.259, ILAR 0.851). With the addition of serum IL-18 levels ≥ 4,800 pg/mL, the sensitivity of the ILAR criteria and specificity of the PRINTO criteria were improved to 1.000 and 1.000, respectively. PRINTO plus serum IL-18 levels ≥ 4,800 pg/mL showed the highest value in Youden’s index (sensitivity – [1 − specificity]). ConclusionSerum IL-18 levels could improve the diagnostic performance of the PRINTO and ILAR criteria for s-JIA. The PRINTO criteria plus serum IL-18 levels ≥ 4,800 pg/mL could be the best diagnostic performance for s-JIA.

Erythropoiesis signature and ubiquitin-mediated proteolysis are enriched in systematic juvenile idiopathic arthritis.

Systemic Juvenile Idiopathic Arthritis (sJIA) is a distinctive subtype of Juvenile Idiopathic Arthritis (JIA). The pathogenesis of sJIA is still unclear with the limited treatment options. Although previous bioinformatics analyses have identified some genetic factors underlying sJIA, these studies were mostly single centre with a small sample size and the results were often inconsistent. Herein, we combined two data sets of GSE20307 and GSE21521 and select the matrix of patients diagnosed as sJIA in it for further analysis. The GSE20307 and GSE21521 matrixes downloaded from the Gene Expression Omnibus (GEO) were analysed using online tools GEO2R, Venny, Metascape, STRING and Cytoscape to identify differentially expressed genes (DEGs), enrichment pathways, protein-protein interaction (PPI), main module and hub genes between sJIA individuals and healthy controls. A total of 289 overlapping genes (consisting of 41 downregulated genes and 248 upregulated genes) were identified. Hub genes were primarily related to erythropoiesis. And the KEGG (Kyoto Encyclopedia of Genes and Genomes) analysis of overlapping DEGs were mainly involved in malaria and non-small cell lung cancer. Besides, DEGs in main module were involved in ubiquitin-mediated proteolysis. Our study suggests that the erythropoiesis signature indeed exists in sJIA similar to previous reports. And ubiquitin-mediated proteolysis is important in sJIA.

In-Depth Serum Proteomics by DIA-MS with In Silico Spectral Libraries Reveals Dynamics during the Active Phase of Systemic Juvenile Idiopathic Arthritis.

In serum proteomics using mass spectrometry, the number of detectable proteins is reduced due to high-abundance proteins, such as albumin. However, recently developed data-independent acquisition mass spectrometry (DIA-MS) proteomics technology has made it possible to remarkably improve the number of proteins in a serum analysis by removing high-abundance proteins. Using this technology, we analyzed sera from patients with systemic juvenile idiopathic arthritis (sJIA), a rare pediatric disease. As a result, we identified 2727 proteins with a wide dynamic range derived from various tissue leakages. We also selected 591 proteins that differed significantly in their active phases. These proteins were involved in many inflammatory processes, and we also identified immunoproteasomes, which were not previously found in serum, suggesting that they may be involved in the pathogenesis of sJIA. A detailed high-depth DIA-MS proteomic analysis of serum may be useful for understanding the pathogenesis of sJIA and may provide clues for the development of new biomarkers.

Application of Weighted Gene Coexpression Network Analysis to Identify Key Modules and Hub Genes in Systemic Juvenile Idiopathic Arthritis.

Systemic juvenile idiopathic arthritis (sJIA) is a severe autoinflammatory disorder with a still not clearly defined molecular mechanism. To better understand the disease, we used scattered datasets from public domains and performed a weighted gene coexpression network analysis (WGCNA) to identify key modules and hub genes underlying sJIA pathogenesis. Two gene expression datasets, GSE7753 and GSE13501, were used to construct the WGCNA. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were applied to the genes and hub genes in the sJIA modules. Cytoscape was used to screen and visualize the hub genes. We further compared the hub genes with the genome-wide association study (GWAS) genes and used a consensus WGCNA to verify that our conclusions were conservative and reproducible across multiple independent datasets. A total of 5,414 genes were obtained for WGCNA, from which highly correlated genes were divided into 17 modules. The red module demonstrated the highest correlation with the sJIA module (r = 0.8, p = 3e−29), whereas the green-yellow module was found to be closely related to the non-sJIA module (r = 0.62, p = 1e−14). Functional enrichment analysis demonstrated that the red module was mostly enriched in the activation of immune responses, infection, nucleosomes, and erythrocytes, and the green-yellow module was mostly enriched in immune responses and inflammation. Additionally, the hub genes in the red module were highly enriched in erythrocyte differentiation, including ALAS2, AHSP, TRIM10, TRIM58, and KLF1. The hub genes from the green-yellow module were mainly associated with immune responses, as exemplified by the genes KLRB1, KLRF1, CD160, and KIRs. We identified sJIA-related modules and several hub genes that might be associated with the development of sJIA. Particularly, the modules may help understand the mechanisms of sJIA, and the hub genes may become biomarkers and therapeutic targets of sJIA in the future.

Unbalanced expression of membrane-bound and soluble programmed cell death 1 and programmed cell death ligand 1 in systemic juvenile idiopathic arthritis

The study aimed to investigate the soluble programmed death-1 (sPD-1) and its ligand (sPD-L1) levels in systemic juvenile idiopathic arthritis (sJIA) patients and elucidate its underlying immunomodulatory mechanisms. Plasma levels of sPD-1, sPD-L1 and related cytokines and proteins were detected using an enzyme-linked immunosorbent assay (ELISA) and Luminex. The effects of PD-1/PD-L1 signal on mDC (myeloid dendritic cell) and IL-6 secretion were measured using flow cytometry. The results revealed decreased levels of sPD-1 in sJIA patients negatively correlated with JADAS-27, PGA, PtGA and CRP. sJIA patients had lower CD86 and MHC-II expression on mDC. When blocking PD-1/PD-L1 signal, IL-6 secretion of DC were increased. Our finding displayed downregulated sPD-1 was related with clinical indicators and could be a new biomarker for sJIA diagnosis. The reduced membrane and soluble forms of PD-1/PD-L1 might take part in sJIA pathogenesis by enhancing mDC proliferation and IL-6 secretion.

Identification of Key Biomarkers and Immune Infiltration in Systemic Juvenile Idiopathic Arthritis by Integrated Bioinformatic Analysis.

Systemic juvenile idiopathic arthritis (sJIA) is a rare and serious type of JIA characterized by an unknown etiology and atypical manifestations in the early stage, and early diagnosis and effective treatment are needed. We aimed to identify diagnostic biomarkers, immune cells and pathways involved in sJIA pathogenesis as well as potential treatment targets. The GSE17590, GSE80060, and GSE112057 gene expression profiles from the Gene Expression Omnibus (GEO) database were screened to obtain differentially expressed genes (DEGs) between sJIA and healthy controls. Common DEGs were subjected to pathway enrichment analysis; a protein-protein interaction network was constructed, and hub genes were identified. In addition, functional annotation of hub genes was performed with GenCLiP2. Immune infiltration analysis was then conducted with xCell, and correlation analysis between immune cells and the enriched pathways identified from gene set variation analysis was performed. The Connectivity Map database was used to identify candidate molecules for treating sJIA patients. Finally, quantitative reverse transcription-polymerase chain reaction (qRT-PCR) was carried out, and the GEO dataset GSE8361 was applied for validation of hub gene expression levels in blood samples from healthy individuals with sJIA. A total of 73 common DEGs were identified, and analysis indicated enrichment of neutrophil and platelet functions and the MAPK pathway in sJIA. Six hub genes were identified, of which three had high diagnostic sensitivity and specificity; ARG1 and PGLYRP1 were validated by qRT-PCR and microarray data of the GSE8361 dataset. We found that increased megakaryocytes and decreased Th1 cells correlated positively and negatively with the MAPK pathway, respectively. Furthermore, MEK inhibitors and some kinase inhibitors of the MAPK family were identified as candidate agents for sJIA treatment. Our results indicate two candidate markers for sJIA diagnosis and reveal the important roles of platelets and the MAPK pathway in the pathogenesis of sJIA, providing a new perspective for exploring potential molecular targets for sJIA treatment.

An Integrative Transcriptomic Analysis of Systemic Juvenile Idiopathic Arthritis for Identifying Potential Genetic Markers and Drug Candidates.

Systemic juvenile idiopathic arthritis (sJIA) is a rare subtype of juvenile idiopathic arthritis, whose clinical features are systemic fever and rash accompanied by painful joints and inflammation. Even though sJIA has been reported to be an autoinflammatory disorder, its exact pathogenesis remains unclear. In this study, we integrated a meta-analysis with a weighted gene co-expression network analysis (WGCNA) using 5 microarray datasets and an RNA sequencing dataset to understand the interconnection of susceptibility genes for sJIA. Using the integrative analysis, we identified a robust sJIA signature that consisted of 2 co-expressed gene sets comprising 103 up-regulated genes and 25 down-regulated genes in sJIA patients compared with healthy controls. Among the 128 sJIA signature genes, we identified an up-regulated cluster of 11 genes and a down-regulated cluster of 4 genes, which may play key roles in the pathogenesis of sJIA. We then detected 10 bioactive molecules targeting the significant gene clusters as potential novel drug candidates for sJIA using an in silico drug repositioning analysis. These findings suggest that the gene clusters may be potential genetic markers of sJIA and 10 drug candidates can contribute to the development of new therapeutic options for sJIA.

Предикторы ответа на терапию генно-инженерными биологическими препаратами у детей с системным ювенильным идиопатическим артритом

Systemic juvenile idiopathic arthritis (sJIA) is a severe orphan autoimmune disease characterized by fever, polymorphic skin rash, hepatosplenomegaly, serositis, generalized lymphadenopathy, and destructive arthritis. Proinflammatory cytokines, including interleukin-1 (IL-1), IL-6, IL-17, IL-18, and tumor necrosis factor (TNF), play a key role in sJIA pathogenesis. sJIA is refractory to conventional immunosuppressive antirheumatic drugs. Before the development of biologicals, sJIA patients had to receive corticosteroids constantly. The implementation of biologicals, such as tocilizumab (IL-6 inhibitor) and canakinumab (IL-1 inhibitor) into clinical practice radically changed the disease course, reduced the need for corticosteroids, and significantly decreased the risk of disability. The administration of biologicals at sJIA onset ensured faster achievement of inactive disease or remission compared to conventional therapy, as well as more patients responding to them. Implementation of biologicals into clinical practice dictated the need to identify optimal conditions for initiating therapy in sJIA patients to improve treatment efficacy and safety. Key words: biologicals, canakinumab, predictors, systemic juvenile idiopathic arthritis, tocilizumab, cytokines

Natural Killer Cells in Systemic Autoinflammatory Diseases: A Focus on Systemic Juvenile Idiopathic Arthritis and Macrophage Activation Syndrome

Natural killer (NK) cells are innate immune lymphocytes with potent cytolytic and immune-regulatory activities. NK cells are well-known for their ability to kill infected and malignant cells in a fast and non-specific way without prior sensitization. For this purpose, NK cells are equipped with a set of cytotoxic molecules such as perforin and apoptosis-inducing proteins. NK cells also have the capacity to produce large amounts of cytokines and chemokines that synergize with their cytotoxic function and that ensure interaction with other immune cells. A less known feature of NK cells is their capacity to kill non-infected autologous cells, such as immature dendritic cells and activated T cells and monocytes. Via the release of large amounts of TNF-α and IFN-γ, NK cells may contribute to disease pathology. Conversely they may exert a regulatory role through secretion of immuno-regulatory cytokines such as GM-CSF, IL-13, and IL-10. Thus, NK cells may be important target and effector cells in the pathogenesis of autoinflammatory diseases, in particular in those disorders associated with a cytokine storm or in conditions where immune cells are highly activated. Key examples of such diseases are systemic juvenile idiopathic arthritis (sJIA) and its well-associated complication, macrophage activation syndrome (MAS). sJIA is a chronic childhood immune disorder of unknown etiology, characterized by arthritis and systemic inflammation, including a daily spiking fever and evanescent rash. MAS is a potentially fatal complication of autoimmune and autoinflammatory diseases, and most prevalently associated with sJIA. MAS is considered as a subtype of hemophagocytic lymphohistiocytosis (HLH), a systemic hyperinflammatory disorder characterized by defective cytotoxic pathways of cytotoxic T and NK cells. In this review, we describe the established features of NK cells and provide the results of a literature survey on the reported NK cell abnormalities in monogenic and multifactorial autoinflammatory disorders. Finally, we discuss the role of NK cells in the pathogenesis of sJIA and MAS.

Regulatory Role for NK Cells in a Mouse Model of Systemic Juvenile Idiopathic Arthritis.

Mice deficient in IFN-γ (IFN-γ knockout [KO] mice) develop a systemic inflammatory syndrome in response to CFA, in contrast to CFA-challenged wild-type (WT) mice who only develop a mild inflammation. Symptoms in CFA-challenged IFN-γ KO resemble systemic juvenile idiopathic arthritis (sJIA), a childhood immune disorder of unknown cause. Dysregulation of innate immune cells is considered to be important in the disease pathogenesis. In this study, we used this murine model to investigate the role of NK cells in the pathogenesis of sJIA. NK cells of CFA-challenged IFN-γ KO mice displayed an aberrant balance of activating and inhibitory NK cell receptors, lower expression of cytotoxic proteins, and a defective NK cell cytotoxicity. Depletion of NK cells (via anti-IL-2Rβ and anti-Asialo-GM1 Abs) or blockade of the NK cell activating receptor NKG2D in CFA-challenged WT mice resulted in increased severity of systemic inflammation and appearance of sJIA-like symptoms. NK cells of CFA-challenged IFN-γ KO mice and from anti-NKG2D-treated mice showed defective degranulation capacities toward autologous activated immune cells, predominantly monocytes. This is in line with the increased numbers of activated inflammatory monocytes in these mice which was particularly reflected in the expression of CCR2, a chemokine receptor, and in the expression of Rae-1, a ligand for NKG2D. In conclusion, NK cells are defective in a mouse model of sJIA and impede disease development in CFA-challenged WT mice. Our findings point toward a regulatory role for NK cells in CFA-induced systemic inflammation via a NKG2D-dependent control of activated immune cells.

Insufficient IL-10 Production as a Mechanism Underlying the Pathogenesis of Systemic Juvenile Idiopathic Arthritis.

Systemic juvenile idiopathic arthritis (sJIA) is a childhood-onset immune disorder of unknown cause. One of the concepts is that the disease results from an inappropriate control of immune responses to an initially harmless trigger. In the current study, we investigated whether sJIA may be caused by defects in IL-10, a key cytokine in controlling inflammation. We used a translational approach, with an sJIA-like mouse model and sJIA patient samples. The sJIA mouse model relies on injection of CFA in IFN-γ-deficient BALB/c mice; corresponding wild type (WT) mice only develop a subtle and transient inflammatory reaction. Diseased IFN-γ-deficient mice showed a defective IL-10 production in CD4+ regulatory T cells, CD19+ B cells, and CD3-CD122+CD49b+ NK cells, with B cells as the major source of IL-10. In addition, neutralization of IL-10 in WT mice resulted in a chronic immune inflammatory disorder clinically and hematologically reminiscent of sJIA. In sJIA patients, IL-10 plasma levels were strikingly low as compared with proinflammatory mediators. Furthermore, CD19+ B cells from sJIA patients showed a decreased IL-10 production, both ex vivo and after in vitro stimulation. In conclusion, IL-10 neutralization in CFA-challenged WT mice converts a transient inflammatory reaction into a chronic disease and represents an alternative model for sJIA in IFN-γ-competent mice. Cell-specific IL-10 defects were observed in sJIA mice and patients, together with an insufficient IL-10 production to counterbalance their proinflammatory cytokines. Our data indicate that a defective IL-10 production contributes to the pathogenesis of sJIA.

Systemic Juvenile Idiopathic Arthritis: Diagnosis and Management.

Systemic juvenile idiopathic arthritis (sJIA) is an inflammatory condition characterized by fever, lymphadenopathy, arthritis, rash and serositis. In sJIA, systemic inflammation has been associated with dysregulation of the innate immune system, suggesting that it is an autoinflammatory disorder. IL-1 and IL-6 play a major role in the pathogenesis of sJIA and treatment with IL-1 and IL-6 inhibitors has shown to be highly effective. Recent data suggests that early cytokine blockage might abrogate chronic, destructive, therapy resistant arthritis phase, reflecting a potential "window of opportunity" in the care of children with sJIA.

IDO1 Deficiency Does Not Affect Disease in Mouse Models of Systemic Juvenile Idiopathic Arthritis and Secondary Hemophagocytic Lymphohistiocytosis.

ObjectivesIndoleamine 2,3-dioxygenase-1 (IDO1) is an immune-modulatory enzyme that catalyzes the degradation of tryptophan (Trp) to kynurenine (Kyn) and is strongly induced by interferon (IFN)-γ. We previously reported highly increased levels of IFN-γ and corresponding IDO activity in patients with hemophagocytic lymphohistiocytosis (HLH), a hyper-inflammatory syndrome. On the other hand, IFN-γ and IDO were low in patients with systemic juvenile idiopathic arthritis (sJIA), an autoinflammatory syndrome. As HLH can occur as a complication of sJIA, the opposing levels of both IFN-γ and IDO are remarkable. In animal models for sJIA and HLH, the role of IFN-γ differs from being protective to pathogenic. In this study, we aimed to unravel the role of IDO1 in the pathogenesis of sJIA and HLH.MethodsWild-type and IDO1-knockout (IDO1-KO) mice were used in 3 models of sJIA or HLH: complete Freund’s adjuvant (CFA)-injected mice developed an sJIA-like syndrome and secondary HLH (sHLH) was evoked by either repeated injection of unmethylated CpG oligonucleotide or by primary infection with mouse cytomegalovirus (MCMV). An anti-CD3-induced cytokine release syndrome was used as a non-sJIA/HLH control model.ResultsNo differences were found in clinical, laboratory and hematological features of sJIA/HLH between wild-type and IDO1-KO mice. As IDO modulates the immune response via induction of regulatory T cells and inhibition of T cell proliferation, we investigated both features in a T cell-triggered cytokine release syndrome. Again, no differences were observed in serum cytokine levels, percentages of regulatory T cells, nor of proliferating or apoptotic thymocytes and lymph node cells.ConclusionsOur data demonstrate that IDO1 deficiency does not affect inflammation in sJIA, sHLH and a T cell-triggered cytokine release model. We hypothesize that other tryptophan-catabolizing enzymes like IDO2 and tryptophan 2,3-dioxygenase (TDO) might compensate for the lack of IDO1.

Mitochondrial and oxidative stress genes are differentially expressed in neutrophils of sJIA patients treated with tocilizumab: a pilot microarray study.

BackgroundVarious pathways involved in the pathogenesis of sJIA have been identified through gene expression profiling in peripheral blood mononuclear cells (PBMC), but not in neutrophils. Since neutrophils are important in tissue damage during inflammation, and are elevated as part of the acute phase response, we hypothesised that neutrophil pathways could also be important in the pathogenesis of sJIA. We therefore studied the gene profile in both PBMC and neutrophils of sJIA patients treated with tocilizumab.MethodsWe studied the transcriptomes of peripheral blood mononuclear cells (PBMC) and neutrophils from eight paired samples obtained from 4 sJIA patients taken before and after treatment, selected on the basis that they achieved ACR90 responses within 12 weeks of therapy initiation with tocilizumab. RNA was extracted and gene expression profiling was performed using Affymetrix GeneChip Human Genome U133 Plus 2.0 microarray platform. A longitudinal analysis using paired t-test (p < 0.05 and FC ≥ 1.5) was applied to identify differentially expressed genes (DEGs) between the two time points followed by ingenuity pathway analysis. Gene Set Enrichment Analysis (GSEA) and quantitative real-time PCR were then performed to verify the microarray results.ResultsGene ontology analysis in neutrophils revealed that response to tocilizumab significantly altered genes regulating mitochondrial dysfunction and oxidative stress (p = 4.6E-05). This was independently verified with GSEA, by identifying a set of oxidative genes whose expression correlated with response to tocilizumab. In PBMC, treatment of sJIA with tocilizumab appeared to affect genes in Oncostatin M signalling and B cell pathways.ConclusionsFor the first time we demonstrate that neutrophils from sJIA patients responding to tocilizumab showed significantly different changes in gene expression. These data could highlight the importance of mitochondrial genes that modulate oxidative stress in the pathogenesis of sJIA.Electronic supplementary materialThe online version of this article (doi:10.1186/s12969-016-0067-7) contains supplementary material, which is available to authorized users.

Altered signaling in systemic juvenile idiopathic arthritis monocytes

Systemic juvenile idiopathic arthritis (sJIA) is characterized by systemic inflammation and arthritis. Monocytes are implicated in sJIA pathogenesis, but their role in disease is unclear. The response of sJIA monocytes to IFN may be dysregulated. We examined intracellular signaling in response to IFN type I (IFNα) and type II (IFNγ) in monocytes during sJIA activity and quiescence, in 2 patient groups. Independent of disease activity, monocytes from Group 1 (collected between 2002 and 2009) showed defective STAT1 phosphorylation downstream of IFNs, and expressed higher transcript levels of SOCS1, an inhibitor of IFN signaling. In the Group 2 (collected between 2011 and 2014), monocytes of patients with recent disease onset were IFNγ hyporesponsive, but in treated, quiescent subjects, monocytes were hyperresponsive to IFNγ. Recent changes in medication in sJIA may alter the IFN hyporesponsiveness. Impaired IFN/pSTAT1 signaling is consistent with skewing of sJIA monocytes away from an M1 phenotype and may contribute to disease pathology.

HLA-DRB1*11 and variants of the MHC class II locus are strong risk factors for systemic juvenile idiopathic arthritis

Systemic juvenile idiopathic arthritis (sJIA) is an often severe, potentially life-threatening childhood inflammatory disease, the pathophysiology of which is poorly understood. To determine whether genetic variation within the MHC locus on chromosome 6 influences sJIA susceptibility, we performed an association study of 982 children with sJIA and 8,010 healthy control subjects from nine countries. Using meta-analysis of directly observed and imputed SNP genotypes and imputed classic HLA types, we identified the MHC locus as a bona fide susceptibility locus with effects on sJIA risk that transcended geographically defined strata. The strongest sJIA-associated SNP, rs151043342 [P = 2.8 × 10(-17), odds ratio (OR) 2.6 (2.1, 3.3)], was part of a cluster of 482 sJIA-associated SNPs that spanned a 400-kb region and included the class II HLA region. Conditional analysis controlling for the effect of rs151043342 found that rs12722051 independently influenced sJIA risk [P = 1.0 × 10(-5), OR 0.7 (0.6, 0.8)]. Meta-analysis of imputed classic HLA-type associations in six study populations of Western European ancestry revealed that HLA-DRB1*11 and its defining amino acid residue, glutamate 58, were strongly associated with sJIA [P = 2.7 × 10(-16), OR 2.3 (1.9, 2.8)], as was the HLA-DRB1*11-HLA-DQA1*05-HLA-DQB1*03 haplotype [6.4 × 10(-17), OR 2.3 (1.9, 2.9)]. By examining the MHC locus in the largest collection of sJIA patients assembled to date, this study solidifies the relationship between the class II HLA region and sJIA, implicating adaptive immune molecules in the pathogenesis of sJIA.

Role of polymorphonucleates in the pathogenesis of systemic juvenile idiopathic arthritis and Still's disease: a proof of concept study

Background Systemic juvenile idiopathic arthritis (sJIA) and adult-onset Still9s disease (AOSD) are autoinflammatory disorders characterized by neutrophilia and abnormal innate immunity response [1]. It has been hypothesized a pathogenic role of neutrophils, because of patients neutrophilia, maybe related to the typical higher production of pro-inflammatory cytokines, like IL-1β, whose role in these disorders should explain the efficacy of IL-1 blockers [2, 3]. IL-1β is synthesized as inactive form and its activation is mediated by the NLRP3 inflammasome [4]. Increased release of this cytokine in the extracellular environment lead to a positive feedback loop that perpetuates and amplifies itself stimulation [5]. This mechanism as well as neutrophils9 activation state could be modified in sJIA and AOSD. Objectives Our aim was to verify possible differences between sJIA and Still9s patients compared to healthy donors, in term of PMNs responsiveness to the extracellular environment and activation state. Methods PMNs were obtained from heparinised venous blood of sJIA patients (n=6), AOSD patients (n=4) and healthy controls (HC, n=8). All patients9 samples were collected during stages of active or non-active disease, according to international disease activity criteria used for the assessment of each disease. After lipopolysaccharide (LPS) treatment, IL-1β content in PMNs supernatants was measured by ELISA assay. CD11b expression levels were measured by flow cytometry, together with intracellular ROS levels through the H 2 DCFDA ROS-indicator. Results In comparison with HC, sJIA PMNs showed an increased IL-1β secretion after LPS stimulation (p Conclusions Data from our proof of concepts study suggest a possible involvement of PMNs in the pathogenesis of sJIA and AOSD, since they seem more active respect healthy ones and more sensitive to pro-inflammatory stimuli. Although further studies are necessary to confirm and validate this hypothesis, the trend observed may have a potential role in the direction of future therapeutic studies. References Pay, S., et al., A multicenter study of patients with adult-onset Still9s disease compared with systemic juvenile idiopathic arthritis. Clin Rheumatol, 2006. 25(5): p. 639-44. Mellins, E.D., et al., Pathogenesis of systemic juvenile idiopathic arthritis: some answers, more questions. Nat Rev Rheumatol, 2011. 7(7): p. 416-26. Mavragani, C.P., et al., Adult-Onset Still9s Disease: From Pathophysiology to Targeted Therapies. Int J Inflam, 2012. 2012: p. 879020. Martinon, F., et al., The inflammasomes: guardians of the body. Annu Rev Immunol, 2009. 27: p. 229-65. Frosch, M., et al., The myeloid-related proteins 8 and 14 complex, a novel ligand of toll-like receptor 4, and interleukin-1beta form a positive feedback mechanism in systemic-onset juvenile idiopathic arthritis. Arthritis Rheum, 2009. 60(3): p. 883-91. Disclosure of Interest None declared

ID: 195: Identification of cytokine cell sources in a new mouse model of systemic juvenile idiopathic arthritis highlights innate immunity of this disorder

Objective: Systemic juvenile idiopathic arthritis (sJIA) is a rheumatic childhood disease, with distinctive systemic inflammatory features and a typical cytokine profile. The etiology of sJIA is largely unknown. Here, we aimed to elucidate the role of specific cell populations and cytokines in the pathogenesis, by means of a new mouse model of sJIA relying on the injection of complete Freund’s adjuvant (CFA) in interferon-gamma deficient (IFN-g KO) mice. Wild type (WT) mice developed a minor inflammation, indicating that IFN-g provides protection in the disease process. Methods: Cytokine mRNA levels were analyzed in organs and purified immune cell populations of CFA-challenged IFN-g KO and WT mice. Cytokine antagonists and cell depleting antibodies were administered to mice. Clinical, laboratory and immune features of sJIA were evaluated. Results: In the diseased IFN-g KO mice, elevated expression of IL 1β, IL-6, IL-17 and IL-22 were found in lymph nodes and – remarkably – also in lung tissue. Gamma-delta T cells were a major cell source for IL-17, and anti-IL-17 antibodies abrogated the disease. In the non-diseased WT mice, expression of IFN-g was almost exclusively found in NK, NKT and gamma-delta T cells. Transient neutralization of IFN-g as well as depletion of NK cells in WT mice both resulted in a fulminant sJIA-like disease. Conclusion: These data pinpoint innate immune cells and non-lymphoid organs as important sources of cytokines in CFA-induced animal models. The results also demonstrate that NK cells provide a regulatory function in the pathogenesis of sJIA, by production of IFN-g.

Higher-dose canakinumab therapy for refractory macrophage activation syndrome in children with systemic juvenile idiopathic arthritis: two case reports

Macrophage activation syndrome (MAS) is a life-threatening, potentially fatal complication of systemic juvenile idiopathic arthritis (sJIA) appears in non-remitted fever, cytopenia, coagulopathy, liver and CNS dysfunctions. Triggers of MAS could be disease activity, infections and medications. Known IL-1 is the key cytokine in pathogenesis of MAS and SJIA, and disease flare associated with increased amounts of different cytokines, especially IL-1β. Many cases of MAS are medically-refractory to traditional doses of cytokine inhibition and may require increased dosing of biologic cytokine blockade. Interleukin-1 (IL-1) is typically a key cytokine in the pathogenesis of sJIA and associated MAS. When MAS occurs in the setting of sJIA treated with IL-1 inhibitors, then increased dosing of IL-1 blockers may be beneficial. This has been shown for anakinra, an IL-1 receptor antagonist, but this drug is currently not available worldwide. Another IL-1 blocker, canakinumbab (CKB), is a monoclonal antibody that blocks IL-1β, but does not also block IL-1α like anakinra. Herein, we describe 2 sJIA patients who developed MAS on standard doses of CKB (4 mg/kg). Both patients received an increased dose of CKB: 150 mg (7.5 and 12.5 mg/kg, respectively) with rapid and complete resolution of MAS. Later the CKB doses was tapered to normal regimen. No side effects or adverse events were noticed during usage of increased CKB doses. Increased dosing of CKB should be considered for CKB-treated sJIA patients who develop MAS on standard dosing.

Recognition systemic juvenile idiopathic arthritis

Systemic juvenile idiopathic arthritis (sJIA) is systemic inflammatory disease classified as a subtype of juvenile idiopathic arthritis(JIA). Besides arthritis, it is characterised by systemic features such as spiking fever, skin rash, hepatosplenomegaly or serositis.It is becoming clear now that abnormalities in the innate immunity [cytokines such as interleukin (IL)-1, IL-6 and IL-18, and neutrophils and monocytes/macrophages rather than lymphocytes]play a major role in the pathogenesis of sJIA, distinguishing it from other JIA subtypes.Another distinctive feature of sJIA is its strong association with macrophage activation syndrome (MAS). Based on this, consensus is emerging that sJIA should be viewed as an autoinflammatory syndrome rather than a classic auto-immune disease.As a consequence of the progression in understanding the underlying mechanisms of sJIA, major changes in the management are evolving.Recently, remarkable improvement has been observed with IL-1 and IL-6 targeted therapies.These therapies might also change the long-term outcome of this disease. Key words: Systemic juvenile idiopathic arthritis; Autoinflammatory syndrome; Abnormalities in the innate immune system; Clinical feature