OBJECTIVETo investigate the changes in the circulating levels of Treg cells in patients with rheumatoid arthritis (RA) and their associations with the disease activity.

METHODSThe fraction of circulating CD4+CD25+FOXP3+ Treg cells in 40 active RA patients and 40 healthy controls were determined by flow cytometry. The serum levels of interleukin-10 (IL-10) and transforming growth factor-β1 (TGF-β1) were measured using enzyme-linked immunosorbent assay, and the expression of Foxp3 mRNA was detected with real-time PCR. The correlation of the changes in the fraction of Treg cells and the disease activity of RA was analyzed.

RESULTSRA patients showed a significantly lower level of circulating Treg cells than the control subjects [(5.36∓1.55)% vs (7.49∓1.46)%, P<0.01]. The expression of Foxp3 mRNA (P<0.01) and serum IL-10 level (P=0.000) were significantly lower, whereas TGF-β1 significantly higher (P=0.000) in RA patients than in the controls. Spearman analysis showed that serum level of IL-10 but not TGF-β1 was correlated to the fraction of Treg cells and Foxp3 mRNA expression, but the fraction of Treg cells was not correlated to such indices of disease activity as tender joint counts, swollen joint counts, visual analog scale, HAQ, disease activity score in 28 joints, ESR, or CRP, nor to RA self-antibodies (including RF and anti-CCP antibodies).

CONCLUSIONA lower fraction and dysfunction of circulating Treg cells might be involved in the pathologies of RA, and a higher disease activity is associated with a greater reduction of Treg cells.