title: The neonatal Fc receptor is expressed by human retinal pigment epithelial cells and is downregulated by tumour necrosis factor-alpha.
abstract: OBJECTIVE
  The neonatal Fc receptor (FcRn) protects immunoglobulin G (IgG) from catabolism, controls its transport between cell layers and extends its serum half-life. In the human, vitreous IgG can be found, but how vitreous IgG is processed or transported is currently unknown. The FcRn is a candidate molecule to regulate these processes. The authors examined FcRn expression and regulation in human retinal pigment epithelium (RPE) cells.
  
  
  METHODS
  In three primary RPE cell cultures (from three donor eyes) and in the human RPE cell line ARPE-19, FcRn and beta-2-microglobulin (β2M) mRNA levels were determined by real-time quantitative PCR. FcRn protein expression was analysed by western blot studies. Stimulation experiments were performed with recombinant human tumour necrosis factor (TNF)-α and interferon (IFN)-γ. HT-29, THP-1 and HeLa cell lines were used as FcRn positive and negative non-ocular controls, respectively.
  
  
  RESULTS
  Expression of FcRn mRNA and protein was demonstrated in all three RPE cultures. After stimulation with TNF-α, FcRn expression is downregulated in RPE cells and upregulated in HT-29 and THP-1 cells. IFN-γ has no effect on FcRn expression in RPE cells.
  
  
  CONCLUSIONS
  Human RPE cells express FcRn. The proinflammatory cytokine TNF-α downregulates FcRn expression. The authors speculate that the FcRn may play a pivotal role in the immune privilege of the human eye.
authors.affiliation: Department of Internal Medicine, Erasmus University Medical Center, Rotterdam, The Netherlands. c.vanbilsen@erasmusmc.nl
authors.forename: Kiki
authors.initials: K
authors.lastname: van Bilsen
authors.forename: P Martin
authors.initials: PM
authors.lastname: van Hagen
authors.forename: Jeroen
authors.initials: J
authors.lastname: Bastiaans
authors.forename: Jan C
authors.initials: JC
authors.lastname: van Meurs
authors.forename: Tom
authors.initials: T
authors.lastname: Missotten
authors.forename: Robert W
authors.initials: RW
authors.lastname: Kuijpers
authors.forename: Herbert
authors.initials: H
authors.lastname: Hooijkaas
authors.forename: Gemma M
authors.initials: GM
authors.lastname: Dingjan
authors.forename: G Seerp
authors.initials: GS
authors.lastname: Baarsma
authors.forename: Willem A
authors.initials: WA
authors.lastname: Dik
mesh_terms: D015153:Blotting, Western; D002460:Cell Line; D002478:Cells, Cultured; D015536:Down-Regulation; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism*; D019073:HT29 Cells; D006367:HeLa Cells; D015395:Histocompatibility Antigens Class I / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D012333:RNA, Messenger / Q000378:metabolism; D011961:Receptors, Fc / Q000235:genetics / Q000378:metabolism*; D055213:Retinal Pigment Epithelium / Q000166:cytology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*; D001613:beta 2-Microglobulin / Q000378:metabolism*
chemical_list: D015395:Histocompatibility Antigens Class I; D012333:RNA, Messenger; D011961:Receptors, Fc; D014409:Tumor Necrosis Factor-alpha; D001613:beta 2-Microglobulin; C100688:Fc receptor, neonatal