Dolphin CCL17 (C-C motif chemokine ligand 17), also known as thymus and activation-regulated chemokine (TARC), is a member of the CC chemokine family involved in regulating Th2-associated immune responses in dolphins (e.g., Tursiops truncatus). CCL17 is produced primarily by dendritic cells, macrophages, endothelial cells, and epithelial cells in response to inflammatory and type 2–associated cytokines. It functions predominantly through the CCR4 receptor to promote chemotaxis and activation of Th2 lymphocytes and regulatory T cells, contributing to modulation of adaptive immune responses and allergic-type inflammation. In healthy dolphins, basal CCL17 expression is expected to be low, but levels may increase during parasitic infections, allergic or hypersensitivity reactions, respiratory inflammation, skin lesions, or systemic immune activation. In marine mammal and comparative immunology research, dolphin CCL17 is of interest as a biomarker of Th2 polarization and immune regulation, providing insight into host responses to environmental stressors, pathogen exposure, and inflammatory disease in both managed and free-ranging dolphin populations.