Expression of CD4⁺ CD25⁺ CD127^low/- T cells in patients with systemic lupus erythematosus

Objective: To detect the new and old surface markers of regulatory T cells (Treg cells) in the CD4⁺ T cells of the patients with systemic lupus erythematosus (SLE) in order to reveal the role of Treg cells in the pathogenesis of SLE. Methods: Peripheral blood samples were collected from 29 newly diagnosed and treatment-naïve SLE patients, 3 males and 26 females, aged (34 ± 13), and 24 sex and aged-matched healthy controls. Three-color flow cytometry was used to detect the CD4⁺ CD25⁺ CD127^{low/ -} T cells, CD4⁺ CD25^high T cells, and CD4⁺ CD25⁺ FOXP3⁺ T cells. The serum anti-nuclear antibody (ANA), anti-ds-DNA antibody, anti-smooth muscle antibody, anti-nucleosome antibody, anti-C1q, C3, and C4 were detected. Blood and urine routine examinations were conducted. Results: The proportion of blood CD4⁺ CD25⁺ CD127^{low/ -} T cells of the SLE patients was not significantly different from that of the controls (P > 0.05), however, the proportions of CD4⁺ CD25⁺ FOXP3⁺ T cells and CD4⁺ CD25^highT cells of the SLE patients were 2.1 ± 1.2 and 0.8 ± 0.4 respectively, both significantly lower than those of the controls (4.0 ± 1.4 and 1.8 ± 0.8 respectively, both P < 0.01). The ratios of the CD4⁺ CD25⁺ CD127^{low/ -} T cells, CD4⁺ CD25^highT cells, and CD4⁺ CD25⁺ FOXP3⁺ T cells to the CD4⁺ CD25⁺ T cells of the SLE patients were 0.5 ± 0.1, 0.1 ± 0, and 0.3 ± 0.1 respectively, all significantly lower than those of the controls (0.6 ± 0.1, 0.2 ± 0.1 and 0.5 ± 0. respectively, all P < 0.01). The level of CD4⁺ CD25⁺ CD127^{low/ -} T cell was positively correlated with the levels of CD4⁺ CD25⁺ FOXP3⁺ T cells and CD4⁺ CD25^highT cell (both P < 0.01). The levels of these 3 kinds of cells and their ratios to CD4⁺ CD25⁺ T cells had no correlation with age, sex, course, IgG, IgA, IgM, urine protein, TIPU, anti-dsDNA, anti-C1q, anti-nuclear body antibody (all P > 0.05), however, were significantly associated negatively with SLE disease activity index, P < 0.05). Only the CD4⁺ CD25⁺ CD127^{low/ -} T cells/CD4⁺ CD25⁺ T cells was negatively correlated with C4 (P < 0.01). Conclusion: The relative ratio of Treg cells to the activated CD4⁺ T cells may play an important role in the pathogenesis of SLE.