Thymus and activation-regulated chemokine (TARC/CCL17) produced by mouse epidermal Langerhans cells is upregulated by TNF-alpha and IL-4 and downregulated by IFN-gamma

Thymus and activation-regulated chemokine (TARC/CCL17) is a Th2-type chemokine and its receptor CC chemokine receptor 4 (CCR4) is preferentially expressed on Th2 cells. Langerhans cells (LC) are immature dendritic cells (DC) in the epidermis of the skin and play vital roles in immune response. In this study, we investigated TARC expression by murine freshly isolated LC and 48 h cultured (mature) LC, and the regulation of TARC production in cultured LC by various cytokines. Murine LC was prepared using a panning method from BALB/c mice. RT-PCR was performed using fresh and cultured LC to evaluate TARC mRNA levels. ELISA was carried out using supernatant of cultured LC to calculate secreted TARC protein levels. TARC mRNA was strongly upregulated during maturation of murine LC. TARC production by murine LC was upregulated by TNF-alpha and IL-4 and downregulated by IFN-gamma, dose-dependently. Th1 and Th2 cytokines reciprocally regulate the production of Th2-type chemokine TARC by murine LC. Th2 cytokine microenvironments in skin may increase TARC production by mature LC, providing attraction of Th2 cells in skin. This may be an amplification circuit in Th2-dominant inflammatory skin disease like atopic dermatitis.