Interleukin 22 and 6 serum concentrations decrease under long-term biologic therapy in psoriasis

Introduction
Psoriasis, affecting approximately 2% of the worldwide population, is a chronic, inflammatory skin disease in which overexpression of proinflammatory cytokines is observed. Most of the available data on the influence of antipsoriatic therapy on the cytokine serum concentration are inconsistent and based on short-term observations.

Aim
To evaluate the influence of long-term biologic therapy with tumor necrosis factor a (TNF-a) blockers (adalimumab, etanercept, infliximab) and IL-12/23 inhibitor (ustekinumab) on the level of IL-6, IL-22 in the sera of patients with psoriasis.

Material and methods
Blood samples were collected from 42 psoriatic patients in order to determine IL-6 and IL-22 serum concentrations prior to and at the 3rd, 12th, 24th and 36th month of biologic therapy. Psoriasis Activity and Severity Index (PASI) was assessed at the same time points. The control group consisted of 30 sex- and age-matched healthy volunteers.

Results
Mean PASI index at baseline was 14.49 ±3.69 and decreased significantly until the end of the observation. Mean IL-6 serum concentration decreased significantly in all study groups (p < 0.05). A statistically significant decrease in IL-22 concentrations was demonstrated during the treatment with adalimumab and infliximab but not etanercept or ustekinumab.

Conclusions
According to obtained results, IL-6 and IL-22 serum concentration may be an accurate marker of response to antipsoriatic therapy, even though not correlated with PASI index. Biologic therapy in psoriasis allows for long-term clinical improvement expressed not only by the remission of skin lesions, but also by lowering serum concentrations of pro-inflammatory interleukins.