Interleukin-20 plays a critical role in maintenance and development of psoriasis in the human xenograft transplantation model.

Background: Interleukin (IL)-20 is a recently discovered cytokine displaying increased levels in psoriatic lesions. Interestingly, IL-20 levels decrease with antipsoriatic treatment, correlating with clinical improvement. However, the role of IL-20 in the aetiology of psoriasis is unknown.

Objectives: In this study, we investigate the effects both of blocking IL-20 signalling in psoriatic plaques and of adding IL-20 to nonlesional psoriasis skin.

Methods: We employed the human skin xenograft transplantation model in which psoriatic plaques and nonlesional keratome skin biopsies obtained from donors with moderate to severe plaque psoriasis were transplanted on to immuno-deficient mice. The transplanted mice were treated with anti-IL-20 antibodies or recombinant human IL-20.

Results: We demonstrate that blocking IL-20 signalling with anti-IL-20 antibodies induces psoriasis resolution and inhibits psoriasis induction. We also demonstrate that continuous IL-20 infusion, together with injection of additional nonactivated leucocytes, promotes induction of psoriasis in nonlesional skin from patients with psoriasis.

Conclusions: The results suggest that IL-20 plays a critical role in the induction and maintenance of psoriasis, and IL-20 is suggested as a new possible specific target in psoriasis treatment.