title: Treatment of rheumatoid arthritis patients with anti-TNF-alpha monoclonal antibody is accompanied by down-regulation of the activating Fcgamma receptor I on monocytes.
abstract: OBJECTIVE
  To study the effect of anti-TNF-alpha therapy on activating IgG Fc receptor (FcgammaR) expression on monocytes of RA patients in relation to changes in disease activity.
  
  
  METHODS
  RA patients were treated with anti-TNF-alpha mAb (infliximab). At baseline, 2 and 14 weeks after the start of anti-TNF-alpha treatment, FcgammaR expression levels on circulating monocytes were evaluated. Changes in expression were correlated to changes in disease parameters. To study the direct effects of TNF-alpha blockade on monocytic FcgammaR expression levels, monocytes were isolated and cultured with anti-TNF-alpha mAb. The effects were compared with those induced by TNF-alpha.
  
  
  RESULTS
  Two weeks after the start of anti-TNF-alpha mAb therapy, monocytic FcgammaRI expression levels were decreased, whereas FcgammaRIIa and IIIa expression levels were unchanged. At 14 weeks, 8 weeks after the last gift of anti-TNF-alpha mAb, FcgammaRI expression levels returned to baseline levels. FcgammaRIIa and IIIa expression levels remained unchanged. The change in FcgammaRI correlated with changes in CRP and ESR levels. In vitro, anti-TNF-alpha mAb treatment did not alter expression of FcgammaRI on monocytes, but increased FcgammaRIIa and IIIa. TNF-alpha down-regulated all activating FcgammaRs, mainly FcgammaRIIa and IIIa, but also the inhibitory FcgammaRIIb.
  
  
  CONCLUSIONS
  Anti-TNF-alpha mAb treatment of RA patients is accompanied by down-regulation of FcgammaRI expression levels on monocytes. This is likely an indirect effect of TNF-alpha blockade on disease activity, since in vitro anti-TNF-alpha mAb does not directly change FcgammaRI expression on monocytes. In contrast, TNF-alpha down-regulated all activating FcgammaRs. Thus, blocking TNF-alpha may relieve the negative feedback mechanism of TNF-alpha as down-regulator of FcgammaRs. Strategies to reduce activating FcgammaRs may have additional value in the treatment of RA patients with TNF-alpha blockade by diminishing immune complex-mediated activation of monocytes/macrophages.
authors.affiliation: Rheumatology & Clinical Immunology, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: S
authors.initials: S
authors.lastname: Wijngaarden
authors.forename: J G J
authors.initials: JG
authors.lastname: van de Winkel
authors.forename: J W J
authors.initials: JW
authors.lastname: Bijlsma
authors.forename: F P J G
authors.initials: FP
authors.lastname: Lafeber
authors.forename: J A G
authors.initials: JA
authors.lastname: van Roon
mesh_terms: D000328:Adult; D000368:Aged; D000911:Antibodies, Monoclonal / Q000627:therapeutic use*; D015703:Antigens, CD / Q000032:analysis; D001172:Arthritis, Rheumatoid / Q000188:drug therapy*; D015536:Down-Regulation; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D000069285:Infliximab; D008297:Male; D008875:Middle Aged; D009000:Monocytes / Q000737:chemistry* / Q000187:drug effects; D017452:Receptors, IgG / Q000032:analysis*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
chemical_list: D000911:Antibodies, Monoclonal; D015703:Antigens, CD; C080568:Fc gamma receptor IIA; D017452:Receptors, IgG; D014409:Tumor Necrosis Factor-alpha; D000069285:Infliximab