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

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.

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.

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.

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.