T-cell compartment in synovial fluid of pediatric patients with JIA correlates with disease phenotype

Introduction Juvenile idiopathic arthritis (JIA) is an autoimmune disease where T cells are key players. It can be classified into two main clinical diseases: polyarticular and pauciarticular, based on the number of joints involved. Oligoarthritis, which is considered a pauciarticular subtype since it involves up to four joints upon presentation, is further divided into persistent or extended forms based on disease progression. Methodology/Principal Findings Here we assessed the Tcell compartment in synovial fluid obtained from 33 JIA patients with active disease and correlated the analyzed parameters with the patients' clinical characteristics. The Tcell compartment was determined by the representation of T-cell receptor (TCR) repertoires and the amount of TCR excision circles (TRECs). Results Patients with polyarticular disease have more a clonal pattern of their TCR repertoire. These findings were consistent in all tested TCR-Vγ consensus primers. Similarly, patients with polyarticular disease had lower TREC levels than patients with pauciarticular disease. A predictive value of TRECs may be suggested, as lower TREC levels were observed in patients in whom disease modifying anti rheumatic drugs were initiated subsequently during the follow-up. Conclusion In pediatric JIA patients, we showed an alteration in the T cells from synovial fluid, which correlated with disease phenotype, assumedly secondary to enhanced proliferation, clonal TCR restriction, and reduced T-cell production, possibly reflecting a different disease or a different course of disease progression.