TNF and psoriasis: Treatment of psoriasis comprises a wide range of options from topical treatments (e.g. local steroid and vitamin D analogues), to heliotherapy (e.g. UVB and PUVA), systemic treatment (e.g. methotrexate, acitretin and cyclosporine), and biological treatment (e.g. anti-TNFα and anti-IL-12/23 antibodies) [14].