The association between the PASI scores and the IL-17 producing cells in lesional skins of psoriatic patients treated with ustekinumab

Abstract

Background: Psoriasis is a common chronic dermatologic condition with unknown pathogenesis. Current studies are pointing toward T helper 1 (Th1) and 17 (Th17) cells induced by interleukin (IL) 12 and 23, respectively. The use of biologic agent ustekinumab, which is an anti IL12/23 monoclonal antibody, proves to be one of the most effective treatment.

Objectives: To determine the association between the Psoriasis Area and Severity Index (PASI) score change during the treatment of ustekinumab and the change of number of IL-17 producing cells biopsied from the lesional skins in psoriatic patients treated with ustekinumab.

Materials and methods: Fourteen psoriatic patients were treated with ustekinumab 45 mg subcutaneously injection at 0, 4, and every 12 weeks for 48 weeks. The PASI scores and 4 mm skin biopsies  were performed in the lesional areas at week 0 and 16 by dermatologists for 48 weeks. The Hematoxylin & Eosin and immunohistochemical staining were done from paraffin embedded sections. The IL-17 positive cells were counted manually in ten different randomized areas under 40X light microsopy. The mean of PASI score and number of IL-17 producing cells were analyzed.

Results: There were significant differences in the term of PASI score and IL-17 producing cells between week 0 and week16 (p<0.01). The study also shows a statistically significant correlation between the percent change of PASI score and cell count (r=0.56, p=0.037).

Summary: The moderate correlation between IL-17 producing cells in lesions and the clinical manifestation assessed by  of PASI scores provides indirect evidence of the mechanism of ustkinumab and the pathogenesis of psoriasis.