title: Disparate lymphoid chemokine expression in mice and men: no evidence of CCL21 synthesis by human high endothelial venules.
abstract: T-cell homing to secondary lymphoid tissues generally depends on chemokine-induced firm adhesion in high endothelial venules (HEVs) and is primarily mediated through the CC chemokine receptor 7 (CCR7) on lymphocytes. The CCR7 ligand designated CCL21 is considered the most important trigger because it appears constitutively expressed by murine HEVs. Surprisingly, when we analyzed human tissues, no CCL21 mRNA could be detected in HEVs. In fact, CCL21 mRNA was only expressed in extravascular T-zone cells and lymphatics, whereas immunostaining revealed CCL21 protein within HEVs. This suggests that T-cell recruitment to human lymphoid tissues depends on the transcytosis of lymphoid chemokines through HEV cells because there is at present no evidence of alternative chemokine production in these cells that could explain the attraction of naive T lymphocytes.
authors.affiliation: Laboratory for Immunohistochemistry and Immunopathology, Institute and Department of Pathology, University of Oslo, Rikshospitalet University Hospital, Norway. hege.carlsen@klinmed.uio.no
authors.forename: Hege S
authors.initials: HS
authors.lastname: Carlsen
authors.forename: Guttorm
authors.initials: G
authors.lastname: Haraldsen
authors.forename: Per
authors.initials: P
authors.lastname: Brandtzaeg
authors.forename: Espen S
authors.initials: ES
authors.lastname: Baekkevold
mesh_terms: D000818:Animals; D001483:Base Sequence; D054421:Chemokine CCL21; D019742:Chemokines, CC / Q000096:biosynthesis* / Q000235:genetics*; D004729:Endothelium, Lymphatic / Q000166:cytology / Q000276:immunology / Q000502:physiology; D015870:Gene Expression; D006801:Humans; D017403:In Situ Hybridization; D042601:Lymphatic Vessels / Q000166:cytology / Q000276:immunology / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D013601:T-Lymphocytes / Q000276:immunology
chemical_list: C515478:CCL21 protein, human; C515479:Ccl21c protein, mouse; D054421:Chemokine CCL21; D019742:Chemokines, CC; D012333:RNA, Messenger