Decreased number of T cells bearing TCR rearrangement excision circles (TREC) in active recent onset systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is characterized by several T lymphocyte abnormalities. An indirect assessment of recent thymus emigrants (RTE) has been recently been made available by measuring the number of TCR recombination excision circles (TREC) in peripheral T cells. We studied TREC levels in peripheral blood mononuclear cells (PBMC) of 32 SLE patients with active disease and 32 normal age- and sex-matched controls. Signal-joint TREC concentration was determined by real-time quantitative-PCR as the number of TREC copies/μg PBMC DNA. SLE patients had lower TREC levels (4.1 ±3.9 ×10 4 TREC/μg DNA) than controls (8.9 ±7.9 ×10 4 /μg DNA) ( P = 0.004). There was an inverse correlation between age and TREC levels in controls ( r = 20.41, P = 0.02) but not in SLE patients. No clinical association was observed between TREC levels and clinical and laboratory SLE manifestations. TREC levels tended to be lower in patients with SLEDAI above 20 than in the rest of the patients ( P = 0.08). The decreased PBMC TREC levels is indicative of a low proportion of RTE in SLE and could be caused by decreased RTE output and/or by increased peripheral T cell proliferation in this disease. The under-representation of RTE in the peripheral T cell pool may play a role in the immune tolerance abnormalities observed in SLE.