In serum and skin lesions of psoriasis patients, IL-17 and IL-22 were showed to promote the expression of antimicrobial peptides in keratinocytes, such as β-defensin-2 (BD-2), S100A7 (psoriasin), cathelicidin (LL37), and S100A8/9 (calprotectin), all of which may lead to the development of psoriasis in individuals with a higher resistance to skin infections (35, 36). Here, IL17A is linked to skin infection.