CD4 and psoriasis: We then tested the proportion of Th17 cells and Treg cells by using flow cytometry and found that the proportion of Th17 cells in the CD4+ T cells population was increased after the stimulation with IL-21 both in psoriasis patients and healthy individuals (Figures 3D,E), whereas the ratio of Treg cells was decreased after stimulation with IL-21 both in healthy individuals and psoriasis patients (Figures 3F,G).