title: Fc gamma receptor CD64 modulates the inhibitory activity of infliximab.
abstract: BACKGROUND
  Tumor necrosis factor (TNF) is an important cytokine in the pathogenesis of inflammatory bowel disease (IBD). Anti-TNF antibodies have been successfully implemented in IBD therapy, however their efficacies differ among IBD patients. Here we investigate the influence of CD64 Fc receptor on the inhibitory activity of anti-TNFs in cells of intestinal wall.
  
  
  METHODS
  Intestinal cell lines, monocytes/macrophages and peripheral blood mononuclear cells (PBMCs) were used as models. The efficacies of adalimumab, infliximab and certolizumab-pegol were assessed by RT-PCR for target genes. Protein levels and localizations were examined by Western blotting and immunofluorescence. Antibody fragments were obtained by proteolytic digestion, immunoprecipitation and protein chip analysis. Knock-down of specific gene expression was performed using siRNAs.
  
  
  RESULTS
  Infliximab had limited efficacy towards soluble TNF in cell types expressing Fc gamma receptor CD64. Both adalimumab and infliximab had lower efficacies in PBMCs of IBD patients, which express elevated levels of CD64. Infliximab-TNF complexes were more potent in activating CD64 in THP-1 cells than adalimumab, which was accompanied by distinct phospho-tyrosine signals. Blocking Fc parts and isolation of Fab fragments of infliximab improved its efficacy. IFN-γ-induced expression of CD64 correlated with a loss of efficacy of infliximab, whereas reduction of CD64 expression by either siRNA or PMA treatment improved inhibitory activity of this drug. Colonic mRNA expression levels of CD64 and other Fc gamma receptors were significantly increased in the inflamed tissues of infliximab non-responders.
  
  
  CONCLUSIONS
  CD64 modulates the efficacy of infliximab both in vitro and ex vivo, whereas the presence of this receptor has no impact on the inhibitory activity of certolizumab-pegol, which lacks Fc fragment. These data could be helpful in both predicting and evaluating the outcome of anti-TNF therapy in IBD patients with elevated systemic and local levels of Fc receptors.
authors.affiliation: Division of Gastroenterology and Hepatology, University Hospital Zurich, Zürich, Switzerland. kacper.wojtal@usz.ch
authors.forename: Kacper A
authors.initials: KA
authors.lastname: Wojtal
authors.forename: Gerhard
authors.initials: G
authors.lastname: Rogler
authors.forename: Michael
authors.initials: M
authors.lastname: Scharl
authors.forename: Luc
authors.initials: L
authors.lastname: Biedermann
authors.forename: Pascal
authors.initials: P
authors.lastname: Frei
authors.forename: Michael
authors.initials: M
authors.lastname: Fried
authors.forename: Achim
authors.initials: A
authors.lastname: Weber
authors.forename: Jyrki J
authors.initials: JJ
authors.lastname: Eloranta
authors.forename: Gerd A
authors.initials: GA
authors.lastname: Kullak-Ublick
authors.forename: Stephan R
authors.initials: SR
authors.lastname: Vavricka
mesh_terms: D000068879:Adalimumab; D000328:Adult; D000911:Antibodies, Monoclonal / Q000494:pharmacology*; D061067:Antibodies, Monoclonal, Humanized / Q000494:pharmacology*; D002460:Cell Line; D002478:Cells, Cultured; D000068582:Certolizumab Pegol; D005260:Female; D006801:Humans; D007140:Immunoglobulin Fab Fragments / Q000494:pharmacology; D015212:Inflammatory Bowel Diseases / Q000378:metabolism; D000069285:Infliximab; D007963:Leukocytes, Mononuclear / Q000187:drug effects / Q000378:metabolism; D008297:Male; D008856:Microscopy, Fluorescence; D008875:Middle Aged; D011092:Polyethylene Glycols / Q000494:pharmacology; D017452:Receptors, IgG / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000276:immunology; D055815:Young Adult
chemical_list: D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D007140:Immunoglobulin Fab Fragments; D017452:Receptors, IgG; D014409:Tumor Necrosis Factor-alpha; D011092:Polyethylene Glycols; D000069285:Infliximab; D000068879:Adalimumab; D000068582:Certolizumab Pegol