PI3 and psoriasis: For example, Tjabringa et al. discovered that skin equivalents stimulated with psoriasis-associated cytokines (IL-1α, TNF-α, and IL-6) displayed the molecular characteristics of psoriatic epidermis such as increased expression of skin-derived anti-leukoprotease (SKALP) and hBD-2 (Tjabringa et al., 2008).