Our recent demonstration [24] that non-viral anti-angiogenic gene therapy alleviated the psoriasis-like phenotype in K5.hTGF-β1 mice (at least by part through downregulation of CD31 expression) indicates that the pro-angiogenic activity of IL-9 may be an important component in the role of this cytokine in psoriasis. The gene discussed is IL9; the disease is psoriasis.