Systemic lupus erythematosus (SLE) patients have a decreased number of peripheral blood T cells containing signal-joint T cell receptor excision circles (Sj TRECs), which are considered an indicator of thymic output. The objective of this study was to investigate the mechanism of the decrease in such T cells. Peripheral blood T cells from SLE patients were classified into CD4+ and CD8+ cells. Sj TREC levels were measured by real-time PCR. Telomerase activity was determined by the telomeric repeat amplification protocol assay. The numbers of Sj TREC containing CD4+ and CD8+ cells were lower in the peripheral blood of SLE patients than in the controls. A correlation was found between the numbers of Sj TREC-positive CD4+ and CD8+ cells. The level of TRECs is influenced by an increase in cell division. To examine this increase, telomerase activity as an indicator of cell division was measured simultaneously; however, there was no correlation between the Sj TREC level and telomerase activity. These results suggest that decreased thymic output occurs in SLE patients.
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