Role of T helper 17 Cells in Allergic Contact Dermatitis

Abstract

Sensitization and elicitation facilitate the development of allergic contact dermatitis (ACD), one of the most common types of dermatitis. Exposure to allergens induces sensitization, after which any re-exposure to the same allergens leads to elicitation and the appearance of ACD. Single re-exposure results in the development of acute ACD, while repeated exposure leads chronic ACD (CACD). Marked epidermal hyperplasia and intense dermal cell infiltration are observed in the early stage of CACD. After the initial establishment of CACD, more repeated exposure induces the late stage of CACD, in which the allergic reactions are ameliorated. T helper (Th) 17 cells, as well as Th1 cells, play crucial roles in the establishment of acute ACD as effector cells, with the former being known to decrease their activity in the early stage of CACD, Th2 dominant condition. Th17-induced cytokines (IL-6, IL-23, transforming growth factor-β1) are simultaneously upregulated in the early stage of CACD. Subsequently, the activity of Th17 increases again in the late stage of CACD, in which Th2 dominant allergic reaction decreases. This relationship between Th17 anf Th2 might induce amelioration of allergic reaction in Th2 dominant CACD. Histamine aggravates CACD by suppressing Th17 response and inducing Th2 response.