The synergistic effect of IL-17 and IL-22 promotes 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 infections70,71. The gene discussed is IL17A; the disease is psoriasis.