Foxp3+Treg in peripheral blood mononuclear cells (PBMCs) tended to be lower in psoriasis patients (Treg/CD4; 4.57±2.40%) than in healthy volunteers (Treg/CD4; 6.00±1.39%) before bath-PUVA therapy, but increased significantly after bath-PUVA therapy in all patients (Treg/CD4; 6.40±2.85%). Here, CD4 is linked to psoriasis.