TNF and psoriasis: M5 cytokines cocktail (IL-17A, IL-22, oncostatin M, IL-1α and TNF-α) was widely used to establish psoriatic cell model, and we chose this model to investigate the role of GPR15LG on the regulation of psoriasis-related cytokines in vitro. First, we confirmed the effective down-regulation of GPR15LG mRNA by shRNAs (Figure 4A).