[A study of T cell recombination excision circles levels in peripheral blood mononuclear cells of systemic lupus erythematosus patients].

Objective: To compare the T cell receptor recombination excision cycle (TREC) levels in peripheral blood mononuclear cells (PBMC) of systemic lupus erythematosus (SLE) patients with normal age- and gender- matched controls. To investigate the correlations between TREC levels of SLE patients and their clinical features.

Methods: We studied TREC levels in peripheral blood mononuclear cells (PBMC) of 21 SLE patients and 22 normal age- and sex-matched controls. TREC concentration was determined by real-time quantitative polymerase chain reaction (real-time qPCR) as the number of TREC copies/1000 PBMCs. The clinical features of the SLE patients such as systemic lupus erythematosus disease activity index (SLEDAI), ESR, C reaction protein (CRP), ANA, anti-dsDNA and complement levels and organ involvement were recorded and assessed.

Results: SLE patients had lower TREC levels [(9.6±7.5) copies/1000 PBMC] than controls [(16.1±11.1) copies/1000 PBMC, P=0.033]. There was an inverse correlation between age and TREC levels in controls (r=-0.614, P=0.002) but not in SLE patients. There was an inverse correlation between SLEDAI and TREC levels in SLE patients (r=-0.656, P=0.001) and TREC levels seemed to have relations to skin lesions (r=-0.620, P=0.003). No other clinical association was observed between TREC levels and clinical and laboratory SLE manifestations.

Conclusion: SLE patients had lower TREC levels than normal controls and there is a tendency that TREC level is reversely correlated with disease activity. The decrease PBMC TREC level is indicative of a low proportion of recent thymic emigrant (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.