TNF and psoriasis: In psoriasis pathogenesis, T-cell-derived interferon (IFN)-γ, IL-17A, and TNF-α stimulate keratinocytes to produce proinflammatory cytokines and chemokines13,27; therefore, we determined whether TG2 is implicated in TNF-α-, IFN-γ-, and IL-17A-induced cytokine production in keratinocytes.