Rat 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 rats (Rattus norvegicus). 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 rats, CCL4 is produced by activated macrophages, dendritic cells, T lymphocytes, epithelial cells, and endothelial cells in response to inflammatory stimuli such as microbial products and cytokines including TNF-α and IL-1β. Rat CCL4 is widely studied in experimental models of neuroinflammation, autoimmune disease, cardiovascular injury, and infectious disease, where chemokine-driven immune cell recruitment contributes to inflammatory signaling and tissue pathology. It has been implicated in models of neuropathic pain, stroke, and central nervous system injury, where CCL4-mediated leukocyte trafficking influences neuroimmune interactions and inflammatory responses in the brain and spinal cord. While CCL4-driven immune cell migration supports host defense and tissue repair, excessive or prolonged expression may contribute to chronic inflammation and tissue damage. Because rats are widely used in neuroscience, pharmacology, and inflammatory disease research, characterization of rat CCL4 supports investigations into CCR5-mediated immune cell trafficking, inflammatory signaling pathways, and host–pathogen interactions relevant to human disease.