Swine CCL4 (C-C motif chemokine ligand 4, also known as MIP-1β, macrophage inflammatory protein-1 beta) is a pro-inflammatory chemokine that regulates recruitment and activation of immune cells during inflammatory and infectious responses in pigs (Sus scrofa domesticus). 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, inflammation, or tissue injury. In pigs, CCL4 is produced by activated macrophages, dendritic cells, epithelial cells, and lymphocytes in response to inflammatory stimuli such as pathogen-associated molecules and cytokines including TNF-α and IL-1β. CCL4-mediated immune cell recruitment is particularly relevant in respiratory and systemic infectious diseases, including porcine reproductive and respiratory syndrome virus (PRRSV), swine influenza virus, and bacterial pathogens involved in porcine respiratory disease complex, where immune cell trafficking to infected tissues contributes to antiviral and antibacterial defense. While CCL4-driven leukocyte migration supports pathogen clearance and immune activation, excessive or prolonged expression may contribute to inflammatory tissue damage, particularly in lung tissue during severe respiratory infections. Because pigs are widely used as large-animal models for human infectious and inflammatory diseases, characterization of swine CCL4 supports studies of chemokine-mediated immune cell migration, host–pathogen interactions, and development of vaccines and immunomodulatory therapies relevant to both veterinary medicine and translational biomedical research.