The chemokine MIP-3 beta is a chemoattractant for T and B lymphocytes, dendritic cells, macrophage progenitor cells, and natural killer cells. It might, therefore, play an important role in the trafficking of T cells in the thymus and migration of T and B cells to secondary lymphoid organs. Furthermore, MIP-3 beta has been recently shown to mediate rapid adhesion of naive CD4(+) T lymphocytes to activated endothelial cells supporting the role of this chemokine in regulation of lymphocyte homing. MIP-3 beta acts through CC chemokine receptor 7 (CCR7). The chemokines Lkn-1 and MIP-3 alpha are also lymphocyte attractants, although compared with MIP- 3 beta, their promigratory effect on lymphocytes is less intensive and their chemotactic activity is more promiscuous. Lkn-1 attracts monocytes, lymphocytes, and eosinophils via the chemokine receptors CCR1 and CCR3. MIP-3 alpha exhibits promigratory effects on lymphocytes, neutrophils, and immature dendritic cells via the CCR6 receptor.