Different results were presented by Fitch et al. [71], Chan et al. [80], Lee et al. [108] and Chamian et al. [111], who reported an increase in p19 mRNA in psoriatic skin compared with healthy skin, as well as an elevated level of p40 in lesional tissues, but not p35, which suggests IL-23 plays a greater role in the pathogenesis of psoriasis than IL-12. Here, IL23A is linked to psoriasis.