Egyptian Rousette Bat (Rousettus aegyptiacus) 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 innate and antiviral immune responses. 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 R. aegyptiacus, CCL4 is likely produced by activated macrophages, dendritic cells, epithelial cells, and lymphocytes following stimulation by pathogen-associated molecules or inflammatory cytokines. This bat species is a known reservoir for viruses such as Marburg virus, making immune mediators like CCL4 important for understanding how immune cell trafficking is regulated during viral infection. Controlled expression of CCL4 may help recruit antiviral immune cells while limiting excessive inflammatory responses, contributing to the ability of Egyptian Rousette bats to tolerate viral infections with minimal pathology. Characterization of Egyptian Rousette Bat CCL4 supports studies of bat antiviral immunity, chemokine signaling, and host–pathogen interactions, providing insights into mechanisms of viral persistence and immune tolerance in natural reservoir hosts.