title: Tumor necrosis factor alpha activates release of B lymphocyte stimulator by neutrophils infiltrating the rheumatoid joint.
abstract: OBJECTIVE
  The tumor necrosis factor (TNF) family member B lymphocyte stimulator (BLyS) is an important regulator of B cell-dependent autoimmunity. Similar to other TNF family members, it is generally expressed as a transmembrane protein and cleaved from the surface to release its active soluble form. This study was undertaken to investigate the expression of BLyS and regulation of BLyS release from the surface of neutrophils infiltrating the rheumatoid joint.
  
  
  METHODS
  BLyS expression was studied in neutrophils from the synovial fluid and peripheral blood of patients with rheumatoid arthritis (RA) and healthy controls, by flow cytometry, Western blotting, and immunofluorescence analyses. Peripheral blood neutrophils cultured with 50% RA synovial fluid were study for membrane expression of BLyS. Neutrophils were exposed to a range of proinflammatory cytokines to study the mechanisms of surface loss of BLyS.
  
  
  RESULTS
  Expression of BLyS was detected on the surface of peripheral blood neutrophils from both RA patients and healthy controls, whereas BLyS expression on synovial fluid neutrophils was very low. Constitutive expression of BLyS was observed in neutrophils, both on the cell membrane and in intracellular stores; however, BLyS release from each of these sites was found to be regulated independently. Of the various cytokine stimuli, only TNFalpha triggered release of BLyS from the neutrophil membrane. This process led to release of physiologically relevant quantities of soluble BLyS, which was dependent on the presence of the pro-protein convertase furin. In contrast, stimulation of neutrophils with granulocyte colony-stimulating factor induced BLyS release from the intracellular stores. Incubation of peripheral blood neutrophils with RA synovial fluid led to TNFalpha-dependent shedding of BLyS from the cell surface.
  
  
  CONCLUSIONS
  These findings indicate that as neutrophils enter the site of inflammation, they release surface-expressed BLyS in a TNFalpha-dependent manner, and thus may contribute to local stimulation of autoimmune B cell responses.
authors.affiliation: Institute of Biomedical Research, University of Birmingham, Birmingham, UK.
authors.forename: Lakhvir K
authors.initials: LK
authors.lastname: Assi
authors.forename: See Heng
authors.initials: SH
authors.lastname: Wong
authors.forename: Andreas
authors.initials: A
authors.lastname: Ludwig
authors.forename: Karim
authors.initials: K
authors.lastname: Raza
authors.forename: Caroline
authors.initials: C
authors.lastname: Gordon
authors.forename: Michael
authors.initials: M
authors.lastname: Salmon
authors.forename: Janet M
authors.initials: JM
authors.lastname: Lord
authors.forename: Dagmar
authors.initials: D
authors.lastname: Scheel-Toellner
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001172:Arthritis, Rheumatoid / Q000378:metabolism* / Q000473:pathology; D015551:Autoimmunity / Q000502:physiology; D053264:B-Cell Activating Factor / Q000235:genetics / Q000378:metabolism*; D001402:B-Lymphocytes / Q000276:immunology; D016022:Case-Control Studies; D002478:Cells, Cultured; D005260:Female; D045683:Furin / Q000502:physiology; D005786:Gene Expression Regulation; D016179:Granulocyte Colony-Stimulating Factor / Q000494:pharmacology; D006801:Humans; D007249:Inflammation; D008297:Male; D008875:Middle Aged; D009504:Neutrophils / Q000166:cytology / Q000378:metabolism* / Q000473:pathology; D013582:Synovial Fluid / Q000166:cytology / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000502:physiology*
chemical_list: D053264:B-Cell Activating Factor; D014409:Tumor Necrosis Factor-alpha; D016179:Granulocyte Colony-Stimulating Factor; D045683:Furin