title: Finding a way out: lymphocyte egress from lymphoid organs.
abstract: The egress of lymphocytes from the thymus and secondary lymphoid organs into circulatory fluids is essential for normal immune function. The discovery that a small-molecule inhibitor of lymphocyte exit, FTY720, is a ligand for sphingosine 1-phosphate (S1P) receptors led to studies demonstrating that S1P receptor type 1 (S1P1) is needed in T cells and B cells for their egress from lymphoid organs. S1P exists in higher concentrations in blood and lymph than in lymphoid organs, and this differential is also required for lymphocyte exit. Transcriptional and post-translational mechanisms regulate S1P1 and thus the egress of lymphocytes. In this review we discuss the body of evidence supporting a model in which lymphocyte egress is promoted by encounter with S1P at exit sites. We relate this model to work examining the effects of S1P receptor agonists on endothelium.
authors.affiliation: Howard Hughes Medical Institute and Department of Microbiology and Immunology, University of California, San Francisco, California 94143, USA. schwab@saturn.med.nyu.edu
authors.forename: Susan R
authors.initials: SR
authors.lastname: Schwab
authors.forename: Jason G
authors.initials: JG
authors.lastname: Cyster
mesh_terms: D002465:Cell Movement / Q000187:drug effects / Q000276:immunology*; D015536:Down-Regulation / Q000187:drug effects / Q000276:immunology; D008196:Lymph / Q000276:immunology; D008214:Lymphocytes / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D008221:Lymphoid Tissue / Q000166:cytology* / Q000187:drug effects / Q000276:immunology; D008246:Lysophospholipids / Q000494:pharmacology; D049349:Receptors, Lysosphingolipid / Q000276:immunology*; D013110:Sphingosine / Q000031:analogs & derivatives / Q000494:pharmacology; D013950:Thymus Gland / Q000166:cytology* / Q000187:drug effects / Q000276:immunology
chemical_list: D008246:Lysophospholipids; D049349:Receptors, Lysosphingolipid; C060506:sphingosine 1-phosphate; D013110:Sphingosine