CD4 and psoriasis: The imbalance between T-helper 1 (Th1) and T-helper 2 (Th2) cells is considered as the main pathogenesis of psoriasis, and growing evidence suggests that T-helper 17 (Th17) cells and CD4+CD25+ regulatory T (Treg) cells play important roles in the pathogenesis of psoriasis [1–4].