6-C-kine (SLC), a Lymphocyte Adhesion-triggering Chemokine Expressed by High Endothelium, Is an Agonist for the MIP-3β Receptor CCR7

The beta chemokine known as 6-C-kine, secondary lymphoid-tissue chemokine (SLC), TCA4, or Exodus-2 (herein referred to as 6CK/SLC) can trigger rapid integrin-dependent arrest of lymphocytes rolling under physiological shear and is highly expressed by high endothelial venules, specialized vessels involved in lymphocyte homing from the blood into lymph nodes and Peyer's patches. We show that 6CK/SLC is an agonist for the lymphocyte chemoattractant receptor, CCR7 (EBI-1, BLR-2), previously described as a receptor for the related beta chemokine MIP-3beta (ELC or Exodus-3). Moreover, 6CK/SLC and MIP-3beta attract the same major populations of circulating lymphocytes, including naive and memory T cells > B cells (but not natural killer cells); desensitization to MIP-3beta inhibits lymphocyte chemotaxis to 6CK/SLC but not to the alpha chemokine SDF-1 (stromal cell-derived factor); and 6CK/SLC competes for MIP-3beta binding to resting mouse lymphocytes. The findings suggest that the majority of circulating lymphocytes respond to 6CK/SLC and MIP-3beta in large part through their common receptor CCR7 and that these molecules may be important mediators of physiological lymphocyte recirculation in vivo.