Changes in cutaneous immune responses, mediated by dendritic cells activated by Toll-like receptors, produce a cascade of cytokines (TNF, IL-17, IL-23, and IL-12), which trigger the hyperproliferation of keratinocytes in the epidermis and give rise to the appearance of epidermal hyperplasia typical of psoriasis, which cause psoriatic lesions. The gene discussed is TNF; the disease is psoriasis.