TNF and psoriasis: Activated and differentiated helper T cell subsets (Th1, Th17, and Th22) and their effector pro-inflammatory cytokine (e.g. TNFα and IL-17A) mediators play a major role in the pathophysiology of psoriasis, promote the synthesis of acute phase proteins and are often associated with extracutaneous and systemic comorbidities (5–8).