Project description:Systemic juvenile idiopathic arthritis (SJIA) is a chronic childhood arthropathy with features of autoinflammation. Early inflammatory SJIA is associated with expansion and activation of neutrophils with a sepsis-like phenotype, but neutrophil phenotypes present in longstanding and clinically inactive disease (CID) are unknown. The objective of this study was to examine activated neutrophil subsets, S100 alarmin release, and gene expression signatures in children with a spectrum of SJIA disease activity. Methods: Highly-purified neutrophils were isolated using a two-step procedure of density-gradient centrifugation followed by magnetic-bead based negative selection prior to flow cytometry or cell culture to quantify S100 protein release. Whole transcriptome gene expression profiles were compared in neutrophils from children with both active SJIA and CID. Results: Patients with SJIA and active systemic features demonstrated a higher number of CD16+CD62Llo neutrophil population compared to controls. This neutrophil subset was not seen in patients with CID or patients with active arthritis not exhibiting systemic features. Using imaging flow cytometry, CD16+CD62Llo neutrophils from patients with active SJIA and features of macrophage activation syndrome (MAS) had increased nuclear hypersegmentation compared to CD16+CD62L+ neutrophils. Serum levels of S100A8/A9 and S100A12 were strongly correlated with peripheral blood neutrophil counts. Neutrophils from active SJIA patients did not show enhanced resting S100 protein release; however, regardless of disease activity, neutrophils from SJIA patients did show enhanced S100A8/A9 release upon PMA stimulation compared to control neutrophils. Furthermore, whole transcriptome analysis of highly purified neutrophils from children with active SJIA identified 214 differentially expressed genes compared to neutrophils from healthy controls. The most significantly upregulated gene pathway was Immune System Process, including AIM2, IL18RAP, and NLRC4. Interestingly, this gene set showed intermediate levels of expression in neutrophils from patients with long-standing CID yet persistent serum IL-18 elevation. Indeed, all patient samples regardless of disease activity demonstrated elevated inflammatory gene expression, including inflammasome components and S100A8. Conclusion: We identify features of neutrophil activation in SJIA patients with active disease and CID, including a proinflammatory gene expression signature, reflecting persistent innate immune activation. Taken together, these studies expand understanding of neutrophil function in chronic autoinflammatory disorders such as SJIA.

Project description:Systemic onset Juvenile Idiopathic Arthritis (SoJIA) represents up to 20% of Juvenile Idiopathic Arthritis (JIA). We have previously reported that this disease is Interleukin 1 (IL1)-mediated, and that IL-1 blockade results in clinical remission in the majority of patients. The diagnosis of SoJIA, however, still relies on clinical findings as no specific diagnostic tests are available, which leads to delays in the initiation of specific therapy. To identify specific diagnostic markers, we analyzed gene expression profiles in 19 pediatric patients with SoJIA during the systemic phase of the disease (fever and/or arthritis), 25 SoJIA patients with no systemic symptoms (arthritis only or no symptoms), 39 healthy controls, 94 pediatric patients with acute viral and bacterial infections (available under GSE6269), 38 pediatric patients with Systemic Lupus Erythematosus (SLE), and 6 patients with a second IL-1 mediated disease known as PAPA syndrome. Statistical group comparison and class prediction identified genes differentially expressed in SoJIA patients compared to healthy children. These genes, however, were also changed in patients with acute infections and SLE. By performing an analysis of significance across all diagnostic groups, we generated a list of 88 SoJIA-specific genes (p<0.01 in SoJIA and >0.5 in all other groups). A subset of 12/88 genes permitted us to accurately classify an independent test set of SoJIA patients with systemic disease. We were also able to identify a group of transcripts that changed significantly in patients undergoing IL-1 blockade. Thus, analysis of transcriptional signatures from SoJIA blood leukocytes can help distinguishing this disease from other febrile illnesses and assessing response to therapy. Availability of accurate diagnostic markers for SoJIA patients may allow prompt initiation of effective therapy and prevention of long-term disabilities. Keywords: Disease state analysis 123 RNA samples extracted from PBMCs were studied. For more details on the clinical information, please refer to the paper (PudMed ID...).

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Neutrophil gene expression in systemic juvenile idiopathic arthritis

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