Orchestrating the orchestrators: chemokines in control of T cell traffic.

The understanding of how chemokines orchestrate the trafficking and activity of immune cells has increased considerably. So far, over 50 chemokines and 20 chemokine receptors have been identified. Detailed analyses have demonstrated the function of chemokine receptors on T cell subsets, the temporal and spatial expression patterns of chemokines in vivo and the phenotypes of animals genetically deficient in one component or several components of the chemokine-chemokine receptor system. New microscopy modalities for studying the influence of chemokines on the migratory activity of T cells in the lymph node have also brought new insights. Here we review such advances with particular emphasis on control of the migration of T cell subsets in lymph nodes and in peripheral tissues in homeostasis and inflammation.