title: Mast cells express IL-17A in rheumatoid arthritis synovium.
abstract: The proinflammatory cytokine IL-17A is considered a crucial player in rheumatoid arthritis (RA) pathogenesis. In experimental models of autoimmune arthritis, it has been suggested that the cellular source of IL-17A is CD4(+) T cells (Th17 cells). However, little is known about the source of IL-17 in human inflamed RA tissue. We explored the cellular sources of IL-17A in human RA synovium. Surprisingly, only a small proportion of IL-17-expressing cells were T cells, and these were CCR6 negative. Unexpectedly, the majority of IL-17A expression colocalized within mast cells. Furthermore, we demonstrated in vitro that mast cells produced RORC-dependent IL-17A upon stimulation with TNF-alpha, IgG complexes, C5a, and LPS. These data are consistent with a crucial role for IL-17A in RA pathogenesis but suggest that in addition to T cells innate immune pathways particularly mediated via mast cells may be an important component of the effector IL-17A response.
authors.affiliation: Division of Infection, Immunity and Inflammation, Glasgow Biomedical Research Centre, University of Glasgow, Glasgow, United Kingdom.
authors.forename: Axel J
authors.initials: AJ
authors.lastname: Hueber
authors.forename: Darren L
authors.initials: DL
authors.lastname: Asquith
authors.forename: Ashley M
authors.initials: AM
authors.lastname: Miller
authors.forename: Jim
authors.initials: J
authors.lastname: Reilly
authors.forename: Shauna
authors.initials: S
authors.lastname: Kerr
authors.forename: Jan
authors.initials: J
authors.lastname: Leipe
authors.forename: Alirio J
authors.initials: AJ
authors.lastname: Melendez
authors.forename: Iain B
authors.initials: IB
authors.lastname: McInnes
mesh_terms: D001172:Arthritis, Rheumatoid / Q000276:immunology* / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D020381:Interleukin-17 / Q000096:biosynthesis / Q000276:immunology*; D008407:Mast Cells / Q000276:immunology* / Q000378:metabolism; D008856:Microscopy, Fluorescence; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013583:Synovial Membrane / Q000276:immunology* / Q000378:metabolism; D016176:T-Lymphocyte Subsets / Q000276:immunology / Q000378:metabolism; D013601:T-Lymphocytes / Q000276:immunology / Q000378:metabolism
chemical_list: C508717:IL17A protein, human; D020381:Interleukin-17