PI3 and psoriasis: In the psoriasis model, Th1 and Th17 cytokines caused thickening of the stratum corneum, which was accompanied by decreases in the mRNA expression of epidermal differentiation proteins filaggrin (FLG) and loricrin (LOR), and upregulation in hBD-2 and SKALP protein expression (Smits et al., 2017).