title: Cytokine mRNA profiling identifies B cells as a major source of RANKL in rheumatoid arthritis.
abstract: OBJECTIVE
  In rheumatoid arthritis (RA), a complex cytokine network drives chronic inflammation and joint destruction. So far, few attempts have been made to identify the cellular sources of individual cytokines systematically. Therefore, the primary objective of this study was systematically to assess the cytokine messenger RNA expression profiles in the five largest cell populations in the synovial fluid and peripheral blood of RA patients. To reflect the in vivo situation as closely as possible, the cells were neither cultured nor stimulated ex vivo.
  
  
  METHODS
  Inflammatory cells from 12 RA patients were sorted into CD4 and CD8 T cells, B cells, macrophages and neutrophils. mRNA expression for 41 cytokines was determined by real-time PCR using microfluidic cards. Receptor activator nuclear factor kappa B ligand (RANKL) (TNFSF11) expression by B cells was further confirmed by flow cytometry and by immunofluorescence staining of frozen sections of synovial tissue from patients with RA.
  
  
  RESULTS
  The detection of cytokines characteristic for T cells and myeloid cells in the expected populations validated this methodology. Beyond the expected cytokine patterns, novel observations were made. Striking among these was the high expression of mRNA for RANKL in B cells from synovial fluid. This observation was validated at the protein level in synovial tissue and fluid.
  
  
  CONCLUSIONS
  RANKL, the key cytokine driving bone destruction by osteoclast activation, is produced by synovial B cells in RA. This observation is of importance for our understanding of the role of B cells in RA and their therapeutic targeting.
authors: MRC Centre for Immune Regulation, Institute for Biomedical Research, College of Medical and Dental Sciences, University of Birmingham, Birmingham, UK.
authors: Lorraine
authors: L
authors: Yeo
authors: Kai-Michael
authors: KM
authors: Toellner
authors: Mike
authors: M
authors: Salmon
authors: Andrew
authors: A
authors: Filer
authors: Christopher D
authors: CD
authors: Buckley
authors: Karim
authors: K
authors: Raza
authors: Dagmar
authors: D
authors: Scheel-Toellner
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001172:Arthritis, Rheumatoid / Q000235:genetics / Q000276:immunology*; D001402:B-Lymphocytes / Q000276:immunology*; D016207:Cytokines / Q000096:biosynthesis* / Q000235:genetics; D005260:Female; D020869:Gene Expression Profiling / Q000379:methods; D006801:Humans; D008297:Male; D008875:Middle Aged; D020411:Oligonucleotide Array Sequence Analysis / Q000379:methods; D016133:Polymerase Chain Reaction / Q000379:methods; D053245:RANK Ligand / Q000096:biosynthesis*; D012333:RNA, Messenger / Q000235:genetics; D013583:Synovial Membrane / Q000276:immunology; D016176:T-Lymphocyte Subsets / Q000276:immunology
chemical_list: D016207:Cytokines; D053245:RANK Ligand; D012333:RNA, Messenger; C505688:TNFSF11 protein, human