A number of studies have shown that serum levels of certain cytokines, including Th1 cytokines (TNF-α, IFN-γ, IL-12, IL-8) and Th17 cytokines (IL-23, IL-17) are elevated in patients with psoriasis and correlate with disease severity43, 44, 45. The gene discussed is CXCL8; the disease is psoriasis.