CD4 and systemic lupus erythematosus: The increased CD4+Foxp3+ T cells in active SLE patients were mainly derived from thymus-derived Treg (tTreg) cells, as determined by a demethylated TSDR status, and represented a unique phenotype, upregulated expression of CD49d, CD161, and IL-17A, with immunosuppressive ability comparable to that of healthy controls.