CD4 and psoriasis: When the percentages of T17 cells in T-cell subsets were directly compared using human psoriasis skin single-cell RNA sequencing (scRNA-seq) data, T17 cells constituted 2.7% of the CD4+ T-cell cluster, 1.3% of the CD8+ T-cell cluster, 2.4% of the CD161+ T-cell cluster and 0.5% of the Treg cluster (13).