Genetic polymorphisms in IL-12B and one of the IL-23 receptor subunits (IL-23R), have been linked to psoriasis [21], and many of the current therapies used in treating psoriasis, such as narrow-band UVB therapy [22] and administration of Etanercept (soluble TNFα receptor) [23] or Alefacept (an antagonist of T cell activation) [24] all reduce levels of IL-23. This evidence concerns the gene IL23R and psoriasis.