title: Cross-linking of IgGs bound on circulating neutrophils leads to an activation of endothelial cells: possible role of rheumatoid factors in rheumatoid arthritis-associated vascular dysfunction.
abstract: BACKGROUND
  Rheumatoid arthritis is characterized by the presence of circulating auto-antibodies, including rheumatoid factors, which recognize the Fc portion of IgGs. The neutrophil is the most abundant circulating leukocyte and it expresses high levels of FcγRs on its surface. The aim of the present study was to examine the capacity of circulating human neutrophils to be activated by rheumatoid factors and the consequences of these events on endothelium.
  
  
  METHODS
  Neutrophil-bound IgGs were cross-linked with anti-human IgGs to mimick the presence of circulating rheumatoid factors and FcγRs-dependent signalling events and functions were examined. The IgG and IgM composition of rheumatoid factors isolated from the serum of RA patients was characterized. Adhesion of neutrophils to endothelial cells was quantified in response to the addition of rheumatoid factors.
  
  
  RESULTS
  Cross-linking of IgGs bound on neutrophils leads to FcγRs-dependent tyrosine phosphorylation, mobilisation of intracellular calcium and the extracellular release of superoxide anions and lysozyme. Incubation of endothelial cells with the supernatant of activated neutrophils increases ICAM-1 expression and IL-8 production by endothelial cells. Finally, rheumatoid factors enhance neutrophil adhesion to endothelial cells.
  
  
  CONCLUSIONS
  Our results show that activation of neutrophils' FcγRs by rheumatoid factors could participate in rheumatoid arthritis-associated vascular damage.
authors.affiliation: Départements de Microbiologie-Infectiologie et Immunologie et de Médecine, Centre de recherche en rhumatologie et immunologie, Centre de recherche du CHU de Québec, Université Laval, Québec, QC, Canada. emmanuelle.rollet@crchul.ulaval.ca.
authors.forename: Emmanuelle
authors.initials: E
authors.lastname: Rollet-Labelle
authors.forename: Myriam
authors.initials: M
authors.lastname: Vaillancourt
authors.forename: Louis
authors.initials: L
authors.lastname: Marois
authors.forename: Marianna M
authors.initials: MM
authors.lastname: Newkirk
authors.forename: Patrice E
authors.initials: PE
authors.lastname: Poubelle
authors.forename: Paul H
authors.initials: PH
authors.lastname: Naccache
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