Macrophage Inflammatory Protein-3-beta (CCL 19, of the intercrine beta chemokine CC family) is an important secreted chemoattractant for dendritic cells, antigen-engaged B-cells, and effector-memory T-cells, signaling through the CCR7 receptor. It may play a role in promoting encounters between recirculating T-cells and dendritic cells and in the migration of activated B-cells into the T-zone of secondary lymphoid tissues. MIP-3ß specifically binds to chemokine receptor CCR7. MIP-3ß is strongly chemotactic for naive CD4 T-cells and for CD8 T-cells and weakly attractive for resting B-cells and memory CD4 T-cells. There is significant expression in dendritic cells in mesenteric and peripheral lymph nodes, and in spleen (T-cell zone or periarteriolar lymphatic sheath) and Peyer patches, but low expression in thymus. Recombinant mouse MIP-3-beta is a polypeptide chain consisting of 83 amino acids with a molecular weight of 9,200 Daltons.