Decreased recent thymus emigrant number in rheumatoid factor-negative polyarticular juvenile idiopathic arthritis.

ABSTRACT

OBJECTIVES: To determine TCR excision circle (TREC) levels, a marker of recent thymic emigrants, in the peripheral lymphocyte pool of rheumatoid factor-negative (RFØ) polyarticular juvenile idiopathic arthritis (JIA) children. METHODS: We studied TREC levels in peripheral blood mononuclear cells (PBMC) in 30 RFØ polyarticular JIA children with active disease and in 30 age- and gender-matched healthy controls. Signal-joint TREC concentration was determined by real-time quantitative-PCR as the number of TREC copies/microg PBMC DNA gauged by a standard curve with known number of TREC-containing plasmids. RESULTS: TREC levels in PBMC were significantly lower in JIA (4.90 +/- 3.86 x 104 TRECs/microg DNA) as compared to controls (10.45 +/- 8.45 x 104 TRECs/microg DNA, p=0.001). There was an inverse correlation between age and TREC levels in healthy children (r=-0.438, p=0.016) but not in JIA. No clinical association was observed between TREC levels and disease activity and use of oral steroids and methotrexate. CONCLUSIONS: The finding of decreased PBMC TREC levels in RFØ polyarticular JIA children is consistent with a low proportion of recent thymus emigrants. This may interfere with the equilibrium between populations of polyclonal and naïve T cells versus oligoclonal memory auto-reactive T cells and, therefore, may hinder the maintenance of immune tolerance in this disease.