title: Interleukin 17 sustains rather than induces inflammation.
abstract: Interleukin (IL)17 is a novel cytokine that has been suggested to play a key role in sustaining chronic inflammation in autoimmune diseases. Since its discovery, much attention has been given to mediators and factors responsible for the development of IL-17-producing cells while very few studies have investigated the inflammatory properties of this cytokine. Here we aimed to characterize the inflammatory properties of IL-17 and to establish if this cytokine per se can initiate an inflammatory reaction or if its main role is to contribute to the exacerbation of ongoing inflammation. To this aim we used two different mouse models of inflammation: the paw oedema and the airpouch. Interestingly, injection of IL-17 in the hind paw did not cause oedema while administration in the pre-inflamed tissues of 6-day-old air pouches induced a long lasting inflammatory reaction that was sustained between 4 and 24h post-injection. Phenotypic analysis of cellular infiltrates demonstrated selective PMN recruitment in exudates and pouch lining tissues. This event was accompanied by induction of a distinct set of pro-inflammatory cytokines including IL-1beta, IL-6, TNF-alpha and chemokines KC and MCP-1. Co-administration of a neutralizing anti-KC antibody with IL-17 significantly reduced its inflammatory response suggesting a key role for this chemokine in mediating the inflammatory effects of IL-17. In conclusion these results demonstrate that IL-17 does not initiate an inflammatory reaction while, if injected in pre-inflamed tissues, is able to further amplify biochemical and cellular events characteristic of the early stages of the inflammatory reaction.
authors.affiliation: William Harvey Research Institute, Barts and The London School of Medicine, Queen Mary University of London, Charterhouse Square, London EC1M6BQ, UK.
authors.forename: Francesco
authors.initials: F
authors.lastname: Maione
authors.forename: Nikolaos
authors.initials: N
authors.lastname: Paschalidis
authors.forename: Nicola
authors.initials: N
authors.lastname: Mascolo
authors.forename: Neil
authors.initials: N
authors.lastname: Dufton
authors.forename: Mauro
authors.initials: M
authors.lastname: Perretti
authors.forename: Fulvio
authors.initials: F
authors.lastname: D'Acquisto
mesh_terms: D000818:Animals; D001483:Base Sequence; D017931:DNA Primers; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D007249:Inflammation / Q000139:chemically induced* / Q000473:pathology; D020381:Interleukin-17 / Q000494:pharmacology*; D008297:Male; D051379:Mice; D009504:Neutrophils / Q000473:pathology; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D017931:DNA Primers; D020381:Interleukin-17