The T cell chemokine receptor CCR7 is internalized on stimulation with ELC, but not with SLC

ELC and SLC are potent agonists for CCR7, a receptor of up-most importance for the regulation of the homing and traffic of lymphocytes into and within secondary lymphoid tissues. We have studied the effects of both chemokines on receptor re-distribution in T lymphocytes and other CCR7-bearing cells by flow cytometry and by assessing receptor mediated functions. In this pap er we show that ELC and SLC differ fundamentally in the ability to induce t he internalization of their receptor. ELC induced a rapid time- and concent ration-dependent internalization of CCR7 and markedly decreased the ability of CCR7-bearing cells to respond to a second stimulation. No receptor inte rnalization, by contrast, was observed on stimulation with SLC. Receptors t hat were internalized on stimulation with ELC were reexpressed when the cel ls were washed. Re-expression of receptors and consequent reactivation of t he cells was prevented in the presence of ELC, but was not affected in the presence of SLC. These findings could explain how T lymphocytes that enter lymphoid tissues in response to SLC produced by high-endothelial venules ca n subsequently migrate in response to SLC and ELC expressed within the T ce ll areas.