title: Interleukin 15 induces endothelial hyaluronan expression in vitro and promotes activated T cell extravasation through a CD44-dependent pathway in vivo.
abstract: T cell recruitment to extralymphoid tissues is fundamental to the initiation and perpetuation of the inflammatory state during immune and autoimmune responses. Interleukin (IL)-15 is a proinflammatory cytokine whose described functions largely overlap with those of IL-2. The latter is attributable in large part to its binding of the heterotrimeric receptor that contains the beta and gamma chains of the IL-2R in combination with an unique IL-15R alpha chain. However, unlike IL-2, IL-15 and its receptor have a wide tissue and cell type distribution, including endothelial cells. Here, we examine the effect of IL-15 on hyaluronan expression by endothelial cells, and investigate its role in vivo in promoting the extravasation of antigen-activated T cells through a CD44-dependent pathway. The expression of hyaluronan on primary endothelial cells and microvascular endothelial cell lines is induced by IL-15, whereas IL-2 has no such activity. Moreover, intraperitoneal administration of IL-15 or TNF-alpha in the absence of other exogenous proinflammatory stimuli allows the extravasation of superantigen-stimulated T cells into this site in vivo in a CD44-dependent manner. T cell recruitment induced by IL-15 requires expression of an intact IL-2R beta chain, indicating that IL-15 operates in this context through the traditional IL-15R. The results suggest that IL-15 can regulate endothelial cell function and thereby enables a CD44-initiated adhesion pathway that facilitates entry of activated T lymphocytes into inflammatory sites. They further demonstrate a novel role for IL-15 (distinct from any of IL-2) in regulating microvascular endothelial cell adhesive function help to understand the role of IL-15R expression on endothelium, and further support a central position for this cytokine in orchestrating multiple sequential aspects of T cell effector function and therefore chronic inflammatory processes.
authors.affiliation: Department of Pathology, University of Texas, Southwestern Medical Center, Dallas 75235-9072, USA.
authors.forename: P
authors.initials: P
authors.lastname: Estess
authors.forename: A
authors.initials: A
authors.lastname: Nandi
authors.forename: M
authors.initials: M
authors.lastname: Mohamadzadeh
authors.forename: M H
authors.initials: MH
authors.lastname: Siegelman
mesh_terms: D000818:Animals; D002417:Cattle; D002460:Cell Line; D002472:Cell Transformation, Viral; D004730:Endothelium, Vascular / Q000187:drug effects* / Q000378:metabolism; D005434:Flow Cytometry; D006801:Humans; D018960:Hyaluronan Receptors / Q000378:metabolism; D006820:Hyaluronic Acid / Q000096:biosynthesis*; D019409:Interleukin-15 / Q000494:pharmacology*; D007376:Interleukin-2 / Q000494:pharmacology; D008213:Lymphocyte Activation; D051379:Mice; D010529:Peritoneal Cavity / Q000166:cytology; D011401:Promoter Regions, Genetic; D051381:Rats; D053647:Receptors, Interleukin-15; D015375:Receptors, Interleukin-2 / Q000378:metabolism; D013539:Simian virus 40; D013601:T-Lymphocytes / Q000187:drug effects / Q000378:metabolism
chemical_list: D018960:Hyaluronan Receptors; C508024:IL15RA protein, human; C508025:Il15ra protein, mouse; D019409:Interleukin-15; D007376:Interleukin-2; D053647:Receptors, Interleukin-15; D015375:Receptors, Interleukin-2; D006820:Hyaluronic Acid