title: Interaction with activated monocytes enhances cytokine expression and suppressive activity of human CD4+CD45ro+CD25+CD127(low)  regulatory T cells.
abstract: OBJECTIVE
  Despite the high frequency of CD4+ T cells with a regulatory phenotype (CD25+CD127(low) FoxP3+) in the joints of patients with rheumatoid arthritis (RA), inflammation persists. One possible explanation is that human Treg cells are converted into proinflammatory interleukin-17 (IL-17)-producing cells by inflammatory mediators and thereby lose their suppressive function. The aim of this study was to investigate whether activated monocytes, which are potent producers of inflammatory cytokines and are abundantly present in the rheumatic joint, induce proinflammatory cytokine expression in human Treg cells and impair their regulatory function.
  
  
  METHODS
  The presence and phenotype of CD4+CD45RO+CD25+CD127(low) T cells (memory Treg cells) and CD14+ monocytes in the peripheral blood (PB) and synovial fluid (SF) of patients with RA were investigated by flow cytometry. Memory Treg cells obtained from healthy control subjects underwent fluorescence-activated cell sorting and then were cocultured with autologous activated monocytes and stimulated with anti-CD3 monoclonal antibodies. Intracellular cytokine expression, phenotype, and function of cells were determined by flow cytometry, enzyme-linked immunosorbent assay, and proliferation assays.
  
  
  RESULTS
  In patients with RA, the frequencies of CD4+CD45RO+CD25+CD127(low) Treg cells and activated CD14+ monocytes were higher in SF compared with PB. In vitro-activated monocytes induced an increase in the percentage of IL-17-positive, interferon-γ (IFNγ)-positive, and tumor necrosis factor α (TNFα)-positive Treg cells as well as IL-10-positive Treg cells. The observed increase in IL-17-positive and IFNγ-positive Treg cells was driven by monocyte-derived IL-1β, IL-6, and TNFα and was mediated by both CD14+CD16- and CD14+CD16+ monocyte subsets. Despite enhanced cytokine expression, cells maintained their CD25+FoxP3+CD39+ Treg cell phenotype and showed an enhanced capacity to suppress T cell proliferation and IL-17 production.
  
  
  CONCLUSIONS
  Treg cells exposed to a proinflammatory environment show increased cytokine expression as well as enhanced suppressive activity.
authors.affiliation: King's College London, London, UK.
authors.forename: Gina J
authors.initials: GJ
authors.lastname: Walter
authors.forename: Hayley G
authors.initials: HG
authors.lastname: Evans
authors.forename: Bina
authors.initials: B
authors.lastname: Menon
authors.forename: Nicola J
authors.initials: NJ
authors.lastname: Gullick
authors.forename: Bruce W
authors.initials: BW
authors.lastname: Kirkham
authors.forename: Andrew P
authors.initials: AP
authors.lastname: Cope
authors.forename: Frédéric
authors.initials: F
authors.lastname: Geissmann
authors.forename: Leonie S
authors.initials: LS
authors.lastname: Taams
mesh_terms: D000328:Adult; D001172:Arthritis, Rheumatoid / Q000276:immunology* / Q000473:pathology; D015704:CD4 Antigens / Q000378:metabolism; D002450:Cell Communication / Q000276:immunology; D002478:Cells, Cultured; D018920:Coculture Techniques; D016207:Cytokines / Q000378:metabolism*; D005260:Female; D058851:GPI-Linked Proteins / Q000378:metabolism; D006801:Humans; D007108:Immune Tolerance / Q000276:immunology*; D007156:Immunologic Memory / Q000276:immunology*; D016130:Immunophenotyping; D020381:Interleukin-17 / Q000378:metabolism; D053645:Interleukin-2 Receptor alpha Subunit / Q000378:metabolism; D015850:Interleukin-6 / Q000378:metabolism; D053699:Interleukin-7 Receptor alpha Subunit / Q000378:metabolism; D017493:Leukocyte Common Antigens / Q000378:metabolism; D018950:Lipopolysaccharide Receptors / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D009000:Monocytes / Q000166:cytology / Q000276:immunology* / Q000378:metabolism; D017452:Receptors, IgG / Q000378:metabolism; D013583:Synovial Membrane / Q000166:cytology / Q000276:immunology; D050378:T-Lymphocytes, Regulatory / Q000166:cytology / Q000276:immunology* / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: D015704:CD4 Antigens; D016207:Cytokines; C428200:FCGR3B protein, human; D058851:GPI-Linked Proteins; C515924:IL17B protein, human; C508600:IL6 protein, human; D020381:Interleukin-17; D053645:Interleukin-2 Receptor alpha Subunit; D015850:Interleukin-6; D053699:Interleukin-7 Receptor alpha Subunit; D018950:Lipopolysaccharide Receptors; D017452:Receptors, IgG; D014409:Tumor Necrosis Factor-alpha; D017493:Leukocyte Common Antigens