IL17A and psoriasis vulgaris: Therefore, cytokines such as IL-17A, IL-22, IL-23, and TNF-α were found to be elevated in both psoriasis vulgaris and GPP; however, GPP lesions yielded significantly higher IL-1 and IL-36, and lower IL-17A and interferon-gamma (IFN-γ) messenger RNA (mRNA) expressions, than plaque psoriasis lesions [23].