IL17A and psoriasis: More recently, biologics such as etanercept, infliximab, adalimumab, certolizumab pegol, ustekinumab, and secukinumab have also been included in the therapeutic scheme for more severe cases of psoriasis and act by targeting T cells or by blocking proteins such as tumor necrosis factor-alpha (TNF-α) and interleukins (e.g., IL-1, IL-2, IL-6, IL-8, IL-10, IL-12, IL-17, IL-20, IL-22, IL-23, and IL-36), which are some of the most important cytokines responsible for psoriasis symptoms [19,20].