Decreased CD4⁺CD25^+bright T cells in peripheral blood of patients with primary Sjögren's syndrome

CD4⁺CD25^+bright T cells played a crucial role in the suppression of immune response. Recently, decreased levels of CD4 ⁺CD25^+bright T cells in the peripheral blood of patients with systemic lupus erythematosus were reported, suggesting the potential role of CD4⁺CD25^+bright T cells in human autoimmune diseases. Primary Sjögren's syndrome (pSS) is another common human systemic autoimmune disease. The present study aimed to investigate the levels of CD4⁺CD25^+bright T cells in pSS and to correlate their levels with some biomarkers of inflammation and immune activation. Thirty-three patients with pSS and 35 age- and sex-matched normal individuals were enrolled in the study. The flowcytometric method was applied in the measurement of CD4⁺CD25^+bright T cells. The results showed that patients with pSS had statistically lower levels of CD4⁺CD25^+bright T cells than normal controls, expressed either as absolute cell numbers (mean ± SD: 47.07 ± 25.53 cells/mm³ versus 79.55 ± 34.56 cells/mm³, P < 0.001) or as percentages of peripheral blood mononuclear cells (mean ± SD: 2.79 ± 1.06% versus 3.84 ± 1.42%, P < 0.001) or as percentages of CD4⁺ T cells (mean ± SD: 7.85 ± 2.62% versus 11.68 ± 3.78%, P < 0.005). Moreover, there were statistically significant inverse correlations between the levels of CD4⁺CD25^+bright T cells and some parameters of inflammation or immune activation including erythrocyte sedimentation rate, C-reactive protein, IgG and rheumatoid factors. The result suggested that CD4⁺CD25^+bright T cells were likely to play anti-inflammatory and immunosuppressive roles in the pathogenesis of pSS. However, the exact functions of decreased circulating CD4⁺CD25 ^+bright T cells in pSS need further elucidated.