These Th cells, in turn, produce a cascade of cytokines, including IL-17, interferon-gamma (IFN-γ), tumor necrosis factor-alpha (TNF-α), and IL-22, which directly stimulate keratinocyte hyper proliferation and contribute to the inflammatory state characteristic of psoriasis (Lowes et al. 2014). The gene discussed is IL17A; the disease is psoriasis.