CCL17, also known as thymus and activation-regulated chemokine （TARC）, is a small cytokine belonging to the CC chemokine family. It is produced by various cell types, including dendritic cells, macrophages, and endothelial cells, and plays a crucial role in regulating immune cell migration and activation. CCL17/TARC is involved in the recruitment of T cells, particularly T helper type 2 （Th2） cells, to sites of inflammation and is implicated in the pathogenesis of allergic and inflammatory diseases, such as atopic dermatitis and asthma. CCL17/TARC binds to its receptor CCR4 and mediates chemotaxis of CCR4-expressing cells, contributing to the orchestration of immune responses.