Among T lymphocyte-derived cytokines related to psoriasis, TNF-α is the main cytokine trigger of PI3Kδ expression, although IL-22 also sustains PI3Kδ levels in human keratinocytes, supporting a role for PI3Kδ in proliferation and de-differentiation processes induced by IL-22 in diseased skin. This evidence concerns the gene TNF and psoriasis.