IL17A and psoriasis: Activated plasmacytoid dendritic cells by genetic and/or environmental factors produce large amounts of pro‐inflammatory cytokines [(such as interleukin (IL)‐17, IL‐22, IL‐23, IL‐1β, interferon (IFN)‐γ, and tumor necrosis factor (TNF)‐α], which can then trigger the onset of psoriasis.6