IL17A and infection: In predisposed individuals, environmental triggers, such as infections or trauma, can activate innate immune pathways, leading to the production of proinflammatory cytokines, including tumor necrosis factor-alpha (TNF-α), interleukin-17 (IL-17), and interleukin-23 (IL-23), which lead to chronic inflammation and aberrant keratinocyte proliferation in the skin.