title: Immunosurveillance modelled in vitro: naive and memory T cells spontaneously migrate across unstimulated microvascular endothelium.
abstract: As a model for T cell immigration into non-lymphoid tissue we set up an in vitro assay that would allow us to investigate the phenotype of T lymphocytes from peripheral lymph nodes (PLN), mesenteric lymph nodes (MLN) or peripheral blood (PBL) of mice, which were able to spontaneously migrate across unstimulated microvascular endothelium. The transendothelial migrating T cell population was enriched for T lymphocytes expressing a "recently activated/memory' phenotype: LFA-1/CD44/ICAM-1high, but also contained CD45RBhigh and LFA-1low T cells, which in the case of MLN T cells were phenotyped as CD4+ and thus characterized as naive T cells. Transmigrated T cells could be further distinguished from their original populations and from each other by their distinct but heterogeneous expression patterns for L-selectin, alpha 4 beta 7-integrin and PECAM-1. This observation suggests the presence of phenotypically different migratory T cells among MLN, PLN and PBL. Additional studies provided evidence that the capacity to migrate across unstimulated microvascular endothelium was a characteristic of a T cell population that could phenotypically be differentiated from activated T cells. The endothelial cells were found to play an active role in selecting the traversing T cell population, as they controlled the number and phenotype of spontaneously transmigrating T cells. Our studies suggest that the capacity to transmigrate across unstimulated microvascular endothelium and hence to immigrate into non-lymphoid tissue is owned by a phenotypically heterogeneous T cell population, which is enriched for memory T cells but not devoid of naive T cells.
authors.affiliation: Max-Planck-Institut für physiologische, Abt. Molekulare Zellbiologie, Bad Nauheim, Germany.
authors.forename: R K
authors.initials: RK
authors.lastname: Röhnelt
authors.forename: G
authors.initials: G
authors.lastname: Hoch
authors.forename: Y
authors.initials: Y
authors.lastname: Reiss
authors.forename: B
authors.initials: B
authors.lastname: Engelhardt
mesh_terms: D000818:Animals; D002196:Capillaries / Q000166:cytology; D002448:Cell Adhesion; D002461:Cell Line, Transformed; D002465:Cell Movement; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000502:physiology*; D007156:Immunologic Memory; D007157:Immunologic Surveillance; D016130:Immunophenotyping; D008198:Lymph Nodes / Q000166:cytology; D008643:Mesentery / Q000166:cytology / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D016176:T-Lymphocyte Subsets / Q000166:cytology* / Q000276:immunology