Dolphin CCL4 (C-C motif chemokine ligand 4, also known as MIP-1β, macrophage inflammatory protein-1 beta) is a pro-inflammatory chemokine involved in recruitment and activation of immune cells during inflammatory and antiviral immune responses in dolphins, particularly the bottlenose dolphin (Tursiops truncatus). CCL4 primarily signals through the CCR5 receptor, promoting chemotaxis of monocytes, macrophages, dendritic cells, natural killer (NK) cells, and activated T lymphocytes to sites of infection or tissue injury. In dolphins, CCL4 is likely produced by activated macrophages, dendritic cells, epithelial cells, and lymphocytes in response to inflammatory stimuli such as microbial components and cytokines including TNF-α and IL-1β. CCL4-mediated immune cell recruitment may play important roles in responses to respiratory infections, skin lesions, and wound healing, as well as in immune defense against viral and bacterial pathogens affecting marine mammals. Because dolphins are frequently exposed to environmental stressors such as pollutants, harmful algal blooms, and emerging infectious diseases, chemokines like CCL4 may also contribute to regulation of inflammatory responses associated with environmental immunotoxicology. As dolphins serve as sentinel species for marine ecosystem health, characterization of dolphin CCL4 supports research into immune regulation, host–pathogen interactions, and the impacts of environmental stress on marine mammal immune function.