Synovial Fluid Neutrophils From Patients With Juvenile Idiopathic Arthritis Display a Hyperactivated Phenotype

Abstract

Objective. Juvenile idiopathic arthritis (JIA) is the most common rheumatic disease in childhood. The predominant subtypes, oligoarticular and polyarticular JIA, are traditionally considered to be autoimmune diseases with a central role for T cells and autoantibodies. Mounting evidence suggests an important role for neutrophils in JIA pathogenesis. We undertook this study to investigate the phenotypic features of neutrophils present in the blood and inflamed joints of patients.Methods. JIA synovial fluid (SF) and parallel blood samples from JIA patients and healthy children were collected. SF-treated neutrophils from healthy donors and pleural neutrophils from patients with pleural effusion were investigated as controls for SF exposure and extravasation. Multicolor flow cytometry panels allowed for in-depth phenotypic analysis of neutrophils, focusing on the expression of adhesion molecules, activation, and maturation markers and chemoattractant receptors. Multiplex technology was used to quantify cytokines in plasma and SF.Results. SF neutrophils displayed an activated, hypersegmented phenotype with decreased CD62L expression, up-regulation of adhesion molecules CD66b, CD11b, and CD15, and down-regulation of CXCR1/2. An elevated percentage of CXCR4-positive neutrophils was detected in SF from patients. Pleural neutrophils showed less pronounced maturation differences. Strikingly, significant percentages of SF neutrophils showed a profound upregulation of atypical neutrophil markers, including CXCR3, intercellular adhesion molecule 1, and HLA-DR. Conclusion.Our data show that neutrophils in inflamed joints of JIA patients have an activated phenotype. This detailed molecular analysis supports the notion that a complex intertwining between these innate immune cells and adaptive immune events drives JIA.

Neutrophils Lose the Capacity to Suppress T Cell Proliferation Upon Migration Towards Inflamed Joints in Juvenile Idiopathic Arthritis

“…Children with oligoarticular JIA present with persistent, unexplained and often asymmetric arthritis in one to four joints before the age of sixteen, often associated with anti-nuclear autoantibodies (13). We and others have shown that neutrophils in synovial fluid from children with oligoarticular JIA are activated and express atypical neutrophil surface markers (2,5). JIA synovial fluid neutrophils also have impaired phagocytosis and trend towards impaired oxidative burst compared to circulating neutrophils, related to the phenotype shift (2).…”

“…Swollen and painful joints are characteristics of many autoimmune rheumatic diseases. In several of these diseases, neutrophils in synovial fluid of inflamed joints have been found to have altered phenotype and behavior, driving local inflammation (1)(2)(3)(4)(5). Neutrophils are not only pro-inflammatory mediators but also immunoregulators, where one of their immunoregulatory effects is the capacity to suppress T cell proliferation and cytokine production (6)(7)(8)(9).…”

B Cells on the Stage of Inflammation in Juvenile Idiopathic Arthritis: Leading or Supporting Actors in Disease Pathogenesis?

“…The mechanisms of immunopathogenesis of JIA are still poorly understood. JIA categories are complex, heterogeneous, with different contributions of immune system players and effector cells ( 24 , 25 , 58 – 63 ). Indeed, several studies have demonstrated a predominance of adaptive immunity in the pathogenesis of oJIA, pJIA, ERA, and JPsA ( 14 , 17 , 18 , 24 , 25 , 39 , 57 , 64 – 86 ), whereas innate immune responses are the major contributors to disease development and progression in sJIA ( 29 , 59 , 87 – 98 ).…”

Neutrophil Homeostasis and Emergency Granulopoiesis: The Example of Systemic Juvenile Idiopathic Arthritis

“…Additionally, neutrophils express a functionally active membrane-bound RANKL, the ligand for receptor activator of NF-kB (RANK) and so can activate osteoclastogenesis ( 202 ). In the joints of JIA patients, activated neutrophils were abundantly present ( 203 – 205 ) and the presence of S100A12 in synovial fluids from JIA patients ( 189 ) provides evidence for their involvement in disease pathogenesis.…”

“…Whereas one study failed to show an increased number of hypersegmented neutrophils, another study showed, by imaging cytometry, that patients with systemically active disease have increased numbers of hypersegmented neutrophils ( 149 , 184 ). We recently uncovered neutrophil-DC hybrid cells (expressing both neutrophil and DC markers) in the synovial fluid from patients with JIA ( 205 ) that may serve as antigen-presenting cells ( 209 , 210 ), eventually contributing to the arthritic phenotype. Remarkably, neutrophil protease genes (including MMP-8 , and MMP-9 ) could also be found in PBMC microarray datasets of sJIA patients and might reflect the presence of low-density granulocytes in the PBMC fraction, which was confirmed by flow cytometry analysis ( 185 ).…”