IL17A and psoriasis: In addition, the immunological alterations in psoriasis lead to the production of high amounts of various cytokines, including tumor necrosis factor alpha (TNF-α), which is produced by keratinocytes and T cells, as well as interferon-gamma (IFN-γ), interleukin-17A (IL-17A) and interleukin-22 (IL-22), which are produced mainly by T cells.