C4A and psoriasis: Early studies have found that serum levels of nonspecific inflammation markers, including C-reactive protein (CRP), platelet P-selectin, haptoglobin, complement component 3 (C3), and C4 [11,12], as well as some pro-inflammatory cytokines, such as TNF-α, IFN-γ, IL-6, IL-8, IL-12, and IL-18, were increased in psoriasis patients [8].