Mouse CCL19 (C-C motif chemokine ligand 19), also known as macrophage inflammatory protein-3β (MIP-3β) or EBI1 ligand chemokine (ELC), is a member of the CC chemokine family that plays a critical role in lymphocyte trafficking and organization of secondary lymphoid tissues in mice (Mus musculus). CCL19 is produced primarily by stromal cells, dendritic cells, and macrophages within lymph nodes, spleen, and Peyer’s patches, and it signals through the CCR7 receptor to direct migration of naïve T cells, central memory T cells, regulatory T cells, and mature dendritic cells. The CCL19–CCR7 axis is essential for T cell priming, antigen presentation, and maintenance of lymphoid architecture. In healthy mice, CCL19 supports immune surveillance and proper compartmentalization of immune cells; genetic disruption of CCL19 or CCR7 results in impaired lymphocyte homing and defective adaptive immune responses. Expression of CCL19 increases during infection, vaccination, inflammatory stimulation, and tumor development. In biomedical research, mouse CCL19 is widely studied in models of viral and bacterial infection, autoimmune disease (e.g., experimental autoimmune encephalomyelitis and arthritis), transplant rejection, and cancer immunology, where it serves as a key regulator of immune cell trafficking and adaptive immune activation.