title: Induction of interferon-alpha production in plasmacytoid dendritic cells by immune complexes containing nucleic acid released by necrotic or late apoptotic cells and lupus IgG.
abstract: OBJECTIVE
  To investigate the release of interferon-alpha (IFN alpha)-inducing material by necrotic or apoptotic cells, its properties, and the necessity of autoantibodies from systemic lupus erythematosus (SLE) patients for the interferogenic activity.
  
  
  METHODS
  U937 monocytic leukemia cells or peripheral blood mononuclear cells (PBMCs) were rendered necrotic by freeze-thawing or apoptotic by treatment with ultraviolet light. Cell culture supernatants from these cells and IgG from SLE patients (SLE IgG) were added to cultures of normal PBMCs or purified plasmacytoid dendritic cells (PDCs). The importance of nucleic acids for IFN alpha induction was investigated by RNase and DNase treatment. The IFN alpha levels were measured by immunoassay.
  
  
  RESULTS
  Both necrotic and apoptotic U937 cells released material that, combined with SLE IgG, induced IFN alpha production in PDCs. The release from apoptotic cells occurred with a 16-hour delay, in late apoptosis. Also, normal PBMCs released IFN alpha-inducing material, but only during necrosis. The interferogenic activity of the necrotic material required the presence of RNA, while both RNA and DNA were important in the apoptotic material. In both cases, the presence of SLE IgG was necessary, and its activity correlated with the presence of antibodies to RNA-binding proteins, but not anti-DNA antibodies.
  
  
  CONCLUSIONS
  Necrotic and late apoptotic cells release material that, combined with SLE IgG, induces production of IFN alpha in PDCs. The IFN alpha inducers probably consist of immune complexes (ICs) containing RNA and possibly DNA as essential interferogenic components. The presence of such interferogenic ICs could explain the ongoing production of IFN alpha in SLE and could be of etiopathogenic importance.
authors.affiliation: Immunology V, Biomedical Center, Uppsala University, Uppsala, Sweden. tanja.lovgren@medsci.uu.se
authors.forename: Tanja
authors.initials: T
authors.lastname: Lövgren
authors.forename: Maija-Leena
authors.initials: ML
authors.lastname: Eloranta
authors.forename: Ullvi
authors.initials: U
authors.lastname: Båve
authors.forename: Gunnar V
authors.initials: GV
authors.lastname: Alm
authors.forename: Lars
authors.initials: L
authors.lastname: Rönnblom
mesh_terms: D000936:Antigen-Antibody Complex / Q000235:genetics* / Q000276:immunology; D017209:Apoptosis / Q000276:immunology*; D004247:DNA / Q000378:metabolism; D003713:Dendritic Cells / Q000276:immunology* / Q000378:metabolism; D003851:Deoxyribonucleases / Q000494:pharmacology; D005615:Freezing; D006801:Humans; D007074:Immunoglobulin G / Q000378:metabolism; D016898:Interferon-alpha / Q000235:genetics / Q000378:metabolism*; D007963:Leukocytes, Mononuclear / Q000166:cytology / Q000276:immunology; D008180:Lupus Erythematosus, Systemic / Q000276:immunology* / Q000378:metabolism / Q000503:physiopathology; D009336:Necrosis; D012313:RNA / Q000378:metabolism; D012260:Ribonucleases / Q000494:pharmacology; D020298:U937 Cells; D014466:Ultraviolet Rays
chemical_list: D000936:Antigen-Antibody Complex; D007074:Immunoglobulin G; D016898:Interferon-alpha; D012313:RNA; D004247:DNA; D003851:Deoxyribonucleases; D012260:Ribonucleases