Pro-inflammatory cytokines primarily involved in the pathogenesis of psoriasis are mainly produced by T cells (e.g., IL-17, IL-21, IL-22, IFN-γ) and dendritic cells (DCs; e.g., TNF-α, IL-6, IL-20, IL-23, NO), forming a central pathogenic loop with IL-23-producing dendritic cells, IL-17-producing Th17 cells, and activated keratinocytes (KCs) [4,5,6,11]. The gene discussed is TNF; the disease is psoriasis.