Cutaneous Application of Leukotriene B4 as an in vivo Model of Psoriasis-Like Skin Inflammation: An Immunohistological Study

Background: Research has revealed new insights into the pathogenesis of psoriasis, leading to new therapeutic options. So far the order of changes in the pathogenesis of psoriasis is unclear. The responses to cutaneous leukotriene B 4 (LTB 4 ) application have been studied in the past as an in vivo model for inflammation. The aim of the present study is to find out the order of changes of key steps in inflammation, which all have been shown to be involved in mature psoriatic lesions. Objective: To study the dynamics of the consecutive stages of inflammation in challenged skin as a reflection of a psoriasis-like inflammatory response. Methods: We examined the dynamics of epidermal growth control and the key representatives of the innate and acquired immune system during the first 72 h after challenging the skin by LTB 4 application. Results: Interleukin 17-positive (IL-17+) cells dominate the acute phase of inflammation, whereas T-Bet+ cells seem to increase gradually during the entire observation period. This indicates a more important role for IL-17 in the unstable phase of inflammation and a more prominent role for T-Bet+ cells within the chronic phase. Conclusion: The present model is highly reproducible and is useful in studying the dynamics of a psoriasis-like inflammation with respect to key components of immunity. It could provide a useful tool to study the immediate biological effects of new therapies like anti-IL-17 drugs on IL-17 production and effects on cutaneous inflammation and epidermal proliferation in vivo.