title: Driving IL-17⁺ γδ T-cell migration in allergic reactions: a new "inflammatory" role for the "homeostatic" chemokine CCL25.
abstract: Chemokines are traditionally classified as homeostatic or inflammatory depending on whether they direct leukocyte migration in the absence or presence of inflammatory stimuli. CC chemokine ligand (CCL)25, a ligand for CC chemokine receptor (CCR)9, has mostly been characterized as a homeostatic chemokine that determines the migration pathway of T-cell progenitors within the thymus, and the recruitment of various lymphocyte subsets to the intestinal mucosa. In this issue of the European Journal of Immunology, Costa et al. [Eur. J. Immunol. 2012. 42: 1250-1260] describe a new inflammatory role for CCL25/CCR9 in controlling the migration of a subset of γδ T cells committed to IL-17 production (γδ17 cells) in a model of allergic pleurisy. Interestingly, the effect of CCL25 was selective for γδ17 cells, as it did not extend to other γδ or αβ T-cell subsets, and resulted in a specific increase of IL-17 (but not IL-4 or IFN-γ) levels in the allergic pleura. In this commentary, I discuss these results in the context of chemokine-mediated recruitment of γδ T cells to inflammatory sites, and the as yet unclear and controversial role of IL-17 in allergic reactions.
authors.affiliation: Instituto de Medicina Molecular, Faculdade de Medicina da Universidade de Lisboa, Lisboa, Portugal. bssantos@fm.ul.pt
authors.forename: Bruno
authors.initials: B
authors.lastname: Silva-Santos
mesh_terms: D000818:Animals; D019742:Chemokines, CC / Q000276:immunology*; D002634:Chemotaxis, Leukocyte / Q000276:immunology*; D006967:Hypersensitivity / Q000276:immunology*; D016023:Integrins / Q000276:immunology*; D020381:Interleukin-17 / Q000276:immunology*; D013601:T-Lymphocytes / Q000276:immunology*
chemical_list: C491541:Ccl25 protein, mouse; D019742:Chemokines, CC; D016023:Integrins; D020381:Interleukin-17; C071777:integrin alpha4beta7