Feline CCL4 (C-C motif chemokine ligand 4, also known as MIP-1β, macrophage inflammatory protein-1 beta) is a pro-inflammatory chemokine that plays an important role in recruitment and activation of immune cells during inflammatory and antiviral immune responses in cats (Felis catus). 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 cats, CCL4 is produced by activated macrophages, dendritic cells, epithelial cells, and lymphocytes in response to inflammatory stimuli such as microbial products and cytokines including TNF-α and IL-1β. CCL4-mediated immune cell recruitment is particularly relevant in viral infections such as feline immunodeficiency virus (FIV) and feline leukemia virus (FeLV), where CCR5-associated chemokine signaling contributes to antiviral immune responses and regulation of leukocyte trafficking. It is also implicated in inflammatory conditions including feline infectious peritonitis (FIP), where macrophage-driven inflammation plays a central role in disease pathology. While CCL4-driven leukocyte migration supports pathogen clearance and immune activation, excessive or prolonged expression may contribute to inflammatory tissue damage. As a regulator of immune cell trafficking and inflammatory signaling, feline CCL4 is important for studies of host–pathogen interactions, viral immunity, and inflammatory disease mechanisms relevant to feline health and comparative immunology.