In addition to this axis representing the core of psoriasis pathogenesis, upstream cytokines (IFN-α, IFNγ, and TNFα), synergizing cytokines (IL-22 and TNFα), and downstream mediators (IL-8, IL1F9, and CCL20) complete the pathogenic puzzle (Figure 2B). The gene discussed is CCL20; the disease is psoriasis.