IL12B and psoriasis: Interestingly, genetic polymorphisms in IL-12B and one of the IL-23 receptor subunits (IL-23R), have been linked to psoriasis [35] and many of the current therapies used in treating psoriasis, such as narrow-band UVB therapy [36], Etanercept (soluble TNFα receptor) [37] and Alefacept (an antagonist of T cell activation) [38] all reduce levels of IL-23.