title: Internalization of antibodies by endothelial cells via fibronectin implicating a novel mechanism in lupus nephritis.
abstract: BACKGROUND
  One of the crucial events in lupus nephritis is the glomerular deposition of immunoglobulins (Igs), of which pathogenic properties have been proposed mostly to be either type IIor type III allergic reactions. Some of IgG3-producing hybridoma clones established from an MRL/MpTn-gld/gld (MRL/gld) lupus mouse generate wire loop-like lesions in glomeruli resembling lupus nephritis when injected into SCID mice. These clones are useful for analyzing the mechanisms of glomerular deposition of antibodies in lupus nephritis at the monoclonal level.
  
  
  METHODS
  Glomerular lesions of SCID mice injected with the hybridoma clones, 17H8a or 1G3 as control were analyzed by light and electron microscopy. Interaction of the antibodies with human glomerular endothelial cells (HGECs) and human umbilical vein endothelial cells (HUVECs) in vitro was studied by fluorescence microscopy, electron microscopy, and flow cytometry.
  
  
  RESULTS
  Both antibodies did not show any antigen specificity for mouse glomeruli. The glomerular lesions generated by 17H8a, but not by 1G3, contained electron-dense deposits not only in subendothelial regions but also in the cytoplasm of endothelial cells, suggesting internalization of the 17H8a antibodies by endothelial cells. In cell culture studies, internalization of only 17H8a antibodies by HGECs and HUVECs was observed, but the antibodies did not have antigen specificity for both types of endothelial cells. The internalization by HUVECs was mediated by actin polymerization, and it was inhibited by RGDS (Arg-Gly-Asp-Ser) tetrapeptide, antihuman fibronectin and antihuman integrin beta1 monoclonal antibodies.
  
  
  CONCLUSIONS
  The interaction between particular antibodies and endothelial cell surface integrins via fibronectin may be involved in their subsequent internalization by endothelial cells leading to antibody deposition in glomeruli. This may be one of the mechanisms of glomerular injury in lupus nephritis.
authors.affiliation: Department of Pathology, Ehime University School of Medicine, Ehime, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Fujii
authors.forename: Kimihiko
authors.initials: K
authors.lastname: Nakatani
authors.forename: Norimasa
authors.initials: N
authors.lastname: Arita
authors.forename: Mitsuko R
authors.initials: MR
authors.lastname: Ito
authors.forename: Miho
authors.initials: M
authors.lastname: Terada
authors.forename: Tatsuhiko
authors.initials: T
authors.lastname: Miyazaki
authors.forename: Minako
authors.initials: M
authors.lastname: Yoshida
authors.forename: Masao
authors.initials: M
authors.lastname: Ono
authors.forename: Takashi
authors.initials: T
authors.lastname: Fujiwara
authors.forename: Kan
authors.initials: K
authors.lastname: Saiga
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Ota
authors.forename: Haruo
authors.initials: H
authors.lastname: Ohtani
authors.forename: Martin
authors.initials: M
authors.lastname: Lockwood
authors.forename: Takeshi
authors.initials: T
authors.lastname: Sasaki
authors.forename: Masato
authors.initials: M
authors.lastname: Nose
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000493:pharmacokinetics*; D042783:Endothelial Cells / Q000276:immunology / Q000378:metabolism*; D004730:Endothelium, Vascular / Q000166:cytology; D005353:Fibronectins / Q000378:metabolism*; D006825:Hybridomas; D007678:Kidney Glomerulus / Q000166:cytology; D008181:Lupus Nephritis / Q000276:immunology* / Q000378:metabolism*; D051379:Mice; D019463:Mice, Inbred MRL lpr; D016513:Mice, SCID; D011485:Protein Binding / Q000276:immunology; D014471:Umbilical Veins / Q000166:cytology
chemical_list: D000911:Antibodies, Monoclonal; D005353:Fibronectins