title: Cyclical expression of L-selectin (CD62L) by recirculating T cells.
abstract: L-Selectin (CD62L) mediates T-cell entry into lymph nodes. Whether the microenvironment modulates L-selectin expression of T cells during diapedesis and transit is unknown. Therefore, L-selectin expression was determined quantitatively on circulating T cells in blood, lymph nodes and thoracic duct by confocal laser scanning microscopy. We show that in contrast to leukocyte function-associated antigen-1 (CD11a/CD18) and ICAM-1 (CD54), L-selectin expression is cyclically expressed on recirculating T cells. It is reduced to approximately 30% of the blood value during entry across high endothelial venules. Within lymph nodes, CD4(+) T-cell subsets maintain reduced L-selectin expression at a similar level in all compartments (T-cell zone, B-cell zone and medulla). After exit, L-selectin is re-expressed to levels comparable to those of T cells in blood. Apparently, L-selectin levels are not only down-regulated during T-cell activation but also routinely reduced while transmigrating within lymph nodes. L-Selectin down-regulation seems to be ligand independent since it also occurs in the white pulp compartments of the spleen which lack classic L-selectin ligands such as GlyCAM-1 and CD34. In addition, T cells in non-lymphoid organs do not reveal reduced L-selectin levels. Thus, the ability of secondary lymphoid organs to reduce L-selectin expression of T cells prior to activation might be a prerequisite for their characteristic property to induce primary immune responses.
authors.affiliation: Center for Structural and Cell Biology in Medicine, Institute of Anatomy, University of Lübeck, Lübeck, Germany.
authors.forename: Antje
authors.initials: A
authors.lastname: Klinger
authors.forename: Andreas
authors.initials: A
authors.lastname: Gebert
authors.forename: Katja
authors.initials: K
authors.lastname: Bieber
authors.forename: Kathrin
authors.initials: K
authors.lastname: Kalies
authors.forename: Ann
authors.initials: A
authors.lastname: Ager
authors.forename: Eric B
authors.initials: EB
authors.lastname: Bell
authors.forename: Jürgen
authors.initials: J
authors.lastname: Westermann
mesh_terms: D000818:Animals; D002465:Cell Movement / Q000276:immunology / Q000502:physiology; D018799:Intercellular Adhesion Molecule-1 / Q000276:immunology / Q000378:metabolism*; D019041:L-Selectin / Q000096:biosynthesis* / Q000276:immunology; D008198:Lymph Nodes / Q000276:immunology; D016169:Lymphocyte Function-Associated Antigen-1 / Q000276:immunology / Q000378:metabolism*; D008297:Male; D051381:Rats; D013154:Spleen / Q000276:immunology; D016176:T-Lymphocyte Subsets / Q000166:cytology / Q000276:immunology* / Q000378:metabolism
chemical_list: D016169:Lymphocyte Function-Associated Antigen-1; D018799:Intercellular Adhesion Molecule-1; D019041:L-Selectin