title: Concurrent presence of agonistic and antagonistic anti-CD95 autoantibodies in intravenous Ig preparations.
abstract: BACKGROUND
  Although there have been several reports suggesting the presence of physiologic anti-CD95 (Fas, APO-1) autoantibodies in human intravenous Ig (IVIg) preparations, it is still unclear whether and under which conditions these autoantibodies block or stimulate the CD95 receptor.
  
  
  OBJECTIVE
  We examined the effects of IVIg on CD95-mediated apoptosis in CD95-sensitive human blood neutrophils in vitro.
  
  
  METHODS
  The presence of anti-CD95 antibodies was determined by competition assays with flow cytometry. Cell death and apoptosis were assessed by ethidium bromide uptake test and annexin V staining, respectively.
  
  
  RESULTS
  Pretreatment of neutrophils with IVIg prevented binding of FITC-conjugated anti-CD95 mAb to the cell surface, suggesting that IVIg contains CD95 autoantibodies. By using low concentrations of IVIg (1 to 10 mg/mL), we observed a dose-dependent inhibition of anti-CD95 mAb (CH11)-mediated neutrophil apoptosis. Higher concentrations of IVIg (20 to 50 mg/mL), however, induced neutrophil death and apoptosis in a dose-dependent manner. This effect was partially blocked by soluble CD95 receptors (recombinant Fc-Fas) but not by an anti-CD95 blocking mAb, which was shown to recognize the CH11 epitope of CD95.
  
  
  CONCLUSIONS
  Both agonistic and antagonistic anti-CD95 antibodies are present in IVIg, and the effect on CD95 is dose-dependent. Our findings have potential implications for IVIg treatment, which is intended to target the CD95 receptor.
authors.affiliation: Department of Pharmacology, University of Bern, Bern, Switzerland.
authors.forename: Frank
authors.initials: F
authors.lastname: Altznauer
authors.forename: Stephan
authors.initials: S
authors.lastname: von Gunten
authors.forename: Peter
authors.initials: P
authors.lastname: Späth
authors.forename: Hans-Uwe
authors.initials: HU
authors.lastname: Simon
mesh_terms: D017209:Apoptosis; D001323:Autoantibodies / Q000276:immunology*; D002478:Cells, Cultured; D006801:Humans; D007074:Immunoglobulin G / Q000276:immunology; D016756:Immunoglobulins, Intravenous / Q000276:immunology*; D009504:Neutrophils / Q000276:immunology / Q000502:physiology*; D019014:fas Receptor / Q000276:immunology*
chemical_list: D001323:Autoantibodies; D007074:Immunoglobulin G; D016756:Immunoglobulins, Intravenous; D019014:fas Receptor