T-Cell Compartment in Synovial Fluid of Pediatric Patients with JIA Correlates with Disease Phenotype

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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. Here we assessed the T-cell compartment in synovial fluid obtained from 33 JIA patients with active disease and correlated the analyzed parameters with the patients' clinical characteristics. The T-cell compartment was determined by the representation of T-cell receptor (TCR) repertoires and the amount of TCR excision circles (TRECs). 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. 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.