IL18 and Hyperkeratosis: IL-17 synergizes with Interferon-γ (IFN-γ) and TNF-α to stimulate keratinocyte proliferation and secrete a large number of inflammatory cytokines such as IL-6, TGF-β, IL-18, IL-17, IL-12, IL -15, TNF-α, GM-CSF, ICAM-1, etc. These inflammatory cytokines can actively recruit and activate neutrophils, accelerate the accumulation of T cells into the epidermis, leading to epidermal hyperplasia, acanthosis and hyperkeratosis [17,25,26].