IL17A and psoriasis: In psoriasis, dendritic cells secrete interleukin-12 (IL-12) and IL-23, while Th1 cells secrete tumor necrosis factor-alpha (TNF-α) and interferon-gamma (IFN-γ), and Th17 cells secrete interleukin-17 (IL-17) and interleukin-22 (IL-22).