Decreased recent thymus emigrant number is associated with disease activity in systemic lupus erythematosus

T cell receptor excision circle (TREC) is produced during T cell maturation within the thymus, and the number of TREC-bearing cells reflects the proportion of recent thymic emigrants in the peripheral lymphocyte pool. We studied TREC levels in peripheral CD4+ and CD8+ lymphocytes in patients with systemic lupus erythematosus (SLE) with quiescent and with active disease and in age- and sex-matched healthy volunteers.

TREC levels in peripheral CD4+ and CD8+ lymphocytes were determined in 29 patients with quiescent SLE, in 22 with active disease, and in 31 age- and sex-matched healthy volunteers. The number of TREC/microg DNA was determined by real-time polymerase chain reaction gauged by a standard curve with known number of TREC-containing plasmids.

TREC levels in CD4+ and CD8+ cells were lower in patients with active SLE (2.27 +/- 2.05 x 10(4) and 4.14 +/- 4.06 x 10(4) TREC/microg DNA, respectively) compared to quiescent SLE (5.83 +/- 7.41 x 10(4) and 11.24 +/- 15.06 x 10(4) TREC/microg DNA; p = 0.03, p = 0.02, respectively). Patients with active SLE had lower TREC levels in CD4+ T cells than controls (2.27 +/- 2.05 x 10(4) vs 5.64 +/- 4.99 x 10(4) TREC/microg DNA; p = 0.03), but this difference did not reach statistical significance for CD8+ cells (4.14 +/- 4.06 x 10(4) vs 8.77 +/- 8.78 x 10(4) TREC/microg DNA; p = 0.1). Patients with quiescent SLE presented TREC levels similar to controls in CD4+ and CD8+ cells (p = 0.49, p = 0.3, respectively).

Our results reveal decreased TREC levels in the peripheral blood of patients with active but not in patients with quiescent SLE. These data suggest that TREC levels are affected by disease activity in SLE.