IL17A and psoriasis: In the pathogenesis of psoriasis, IL-17 interacts with keratinocytes to promote the production of antimicrobial peptides, proinflammatory cytokines and chemokines (IL-1β, TNF-α, IL-6, IL-17C, CXCL1, CXCL3, CXCL5, CXCL8 [IL-8] and CCL20) and proliferative cytokines (IL-19) (55, 109, 110).