Functions of Langerhans cells in diisononyl phthalate-aggravated allergic contact dermatitis

Diisononyl phthalate (DINP), a widely-used plasticizer, is associated with the development of allergic diseases including allergic contact dermatitis (ACD). Langerhans cells (LCs) are reported to be involved in the sensitization phase of ACD. However, the effect of skin DINP exposure on ACD in C57BL/6 mice and the functions of LCs remain unclear. Our results showed that DINP aggravated ACD in C57BL/6 mice, which was paralleled by ear thickening, mast cell degranulation, expressions of immunological cytokines, including IL-4, IL-5, IL-13, IL-17, IL-6, IL-1β, transforming growth factor (TGF)-β1 in the ear, serum and submaxillary lymph nodes (SMLN) and thymic stromal lymphopoietin (TSLP) in the ear. DINP activated LCs through enhancing antigen-uptake by LCs in ear epidermis and stimulated the migratory DC via elevating the expression of surface molecules, including CD86, CD80, PD-L1 and PD-L2 in SMLN. Ablation of LCs promoted the enhancement effect of DINP on ACD and Th2/Th17 responses, suggesting that LCs may not be essential for DINP-related ACD and Th2/Th17 responses. In conclusion, DINP aggravates ACD through activating LCs, enhancing mDC function and mast cell degranulation, promoting Th2/Th17 responses, and stimulating the expression of immunological cytokines. DINP is responsible for the prevalence of ACD and inhibiting Th2/Th17 cell response may be a new therapeutic strategy.