Increased proportions of CD4+CD25-Foxp3+T cells in patients with active systemic lupus erythematosus (SLE). Proportions of CD4+CD25-Foxp3+ T cells were analyzed by fluorescence-activated cell sorting (FACS) in SLE patients and healthy controls (HC). (a) A significant increase in the percentage of CD4+CD25-Foxp3+ T cells was observed in SLE patients (n = 61) as compared to HC (n = 36) (P <0.0001). (b) The proportion of Helios + cells was significantly reduced in CD4+CD25-Foxp3+ T cells from SLE patients as compared to CD4+CD25+Foxp3+ T cells from HC (P <0.0001) and SLE patients (P <0.0001). (c) Percentage (P = 0.01) as well as absolute numbers (P = 0.039) of CD4+CD25-Foxp3+ T cells were significantly increased in patients with active SLE as compared to patients with inactive SLE. (d) A significant correlation was observed for the percentage of CD4+CD25-Foxp3+ T cells and the SLE disease activity index (SLEDAI) (r = 0.5; P <0.001), European Consensus Lupus Activity Measurement (ECLAM) (r = 0.54; P <0.001) and SLE index score (SIS) score (r = 0.5; P <0.001), as well as the levels of dsDNA antibodies (r = 0.4; P <0.001), C3 (r = 0.3; P = 0.01) and CH50 (r = 0.3; P = 0.01). *Significant differences.