IL17F and psoriasis: Many inflammatory cells and cytokines are involved in the pathogenesis of the disease.1, 2 Tumor necrosis factor (TNF)-α, interferon (IFN)-α, IFN-g, interleukin (IL)-1β, IL-6, IL-12, IL-17A, IL-17F, IL-22, and IL-23 from various immune cells, primarily T helper type 1 (Th1) and type 17 (Th17) cells, also contribute to the pathophysiology of psoriasis, as well as keratinocytes, other T cells, and dendritic cells.13