TNFSF12 and psoriasis: In addition, TWEAK deficiency in mice results in defective maintenance of psoriasis-specific T helper type17 (Th17) cells in the skin, and impairs the expression of disease-characteristic cytokines such as chemokine (C-C motif) ligand 20 and interleukin-19 (IL-19) in a murine psoriasis-like model13.