Abstract
Para-Phenylenediamine (PPD) is an aromatic amine used in hair dyes and in temporary black henna tattoos, which is a frequent cause of allergic contact dermatitis (ACD). ACD is a skin inflammatory reaction characterized by modifications such as spongiosis, exocytosis and acanthosis. The aim of this study is to characterize the expression and the role of IL-20-related cytokines, including IL-19, IL-20, IL-22 and IL-24, in ACD. The expression of IL19, IL20, IL22 and IL24 is increased in affected skin from PPD allergic patients compared with uninvolved skin. In addition, the expression of these cytokines positively correlates with clinical symptoms. To assess their role in ACD, we set up a mouse model of PPD-induced allergic contact dermatitis and we showed that, in contrast to Il22-deficient mice, Il22ra1-, Il20rb- and Il24-deficient mice are partially protected against development of PPD-induced contact hypersensitivity. These mice have decreased ear thickening and less acanthosis compared with WT mice after PPD treatment. In addition, the absence of IL-22R, IL-20R2 or IL-24 affects the recruitment of neutrophils into the skin but not the total IgE production. Taken together, these results demonstrate the implication of IL-24 via the IL-20R type II receptor in the inflammatory process of ACD.
Highlights
Para-Phenylenediamine (PPD) is an aromatic amine used in hair dyes and in temporary black henna tattoos[1]
We evaluated the expression of IL-20 subfamily cytokines in patients diagnosed for PPD-induced allergic contact dermatitis (ACD)
Il20 was not significantly affected and Il22 expression was only upregulated in CD45-positive cells, at a later time point (Fig. 2B). Taken together these results indicate that expression of Il19, Il22 and Il24 are quickly upregulated after PPD treatment, and non-hematopoietic cells represent the main source of IL-19 and IL-24 whereas CD45+ cells produce IL-22
Summary
Para-Phenylenediamine (PPD) is an aromatic amine used in hair dyes and in temporary black henna tattoos[1]. Subsequent contact with the same allergen will induce strong T cell responses and recruitment of these hapten-specific T lymphocytes in the skin, which, in turn, will lead to the epidermal changes described above[6]. Because IL-20-related cytokines are known to play an important role in skin inflammatory diseases such as psoriasis[11], they could be actors in the ACD reaction. IL-20-related cytokines are produced by immune cells such as monocytes and T lymphocytes and are involved in the maintenance of the epidermal barrier integrity by promoting antimicrobial peptide production, chemokine expression and keratinocyte proliferation[11]. These cytokines play redundant roles because they share common receptor complexes. IL-22 signals through a complex composed of an IL-22R subunit and IL-10R2
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