Feline CCL17 (C-C motif chemokine ligand 17), also known as thymus and activation-regulated chemokine (TARC), is a member of the CC chemokine family that plays a key role in regulating Th2-associated immune responses in cats (Felis catus). CCL17 is produced primarily by dendritic cells, macrophages, endothelial cells, and epithelial cells in response to inflammatory cytokines, particularly those associated with type 2 immunity. It functions mainly through the CCR4 receptor to promote chemotaxis and activation of Th2 lymphocytes and regulatory T cells, contributing to allergic inflammation and immune modulation. In healthy cats, basal CCL17 expression is typically low, but levels may increase during allergic diseases such as feline atopic dermatitis, asthma, and other hypersensitivity conditions, as well as during certain inflammatory or infectious processes. In veterinary and comparative medicine research, feline CCL17 is of particular interest as a biomarker of Th2 polarization and allergic inflammation, providing insight into immune dysregulation, skin and airway disease pathogenesis, and potential targets for immunomodulatory therapies in feline patients.