title: TNFα suppresses IFNγ-induced MHC class II expression on retinal pigmented epithelial cells cultures.
abstract: OBJECTIVE
  One major consequence of retinal pigment epithelium (RPE) cell activation during autoimmune uveitis is the induction of MHC II molecules expression at their surface. IFNγ is regarded as the main cytokine involved in this induction. As TNFα plays a central role in autoimmune uveitis, we investigated its effects on IFNγ-mediated MHC II induction on RPE cells.
  
  
  METHODS
  Retinal pigment epithelium cells (ARPE-19) were stimulated with IFNγ, TNFα and the anti-TNFα antibody infliximab. The expression of MHCII and ICAM-1 was analysed by flow cytometry. The activation and expression of IRF-1 and STAT-1, two proteins involved in IFNγ-signalling pathway, were analysed by WB. Class II transactivator (CIITA) expression was monitored by qRT-PCR and immunoprecipitation.
  
  
  RESULTS
  TNFα inhibits IFNγ-induced MHC II expression on ARPE cells in a dose-dependent manner. Infliximab completely reverses the inhibitory effect of TNFα. We did not observe an inhibitory effect of TNFα on the expression of ICAM-1 induced by IFNγ. Similarly, IFNγ-induced STAT1 phosphorylation and IRF1 expression were not affected by TNFα. On the contrary, we found that TNFα suppresses IFNγ-induced CIITA mRNA accumulation and protein expression.
  
  
  CONCLUSIONS
  TNFα inhibits IFNγ-induced MHC II expression in RPE cells. This inhibitory effect was reversed by infliximab and was not because of a global inhibition of IFNγ -mediated RPE cell activation but rather to a specific down-regulation of CIITA expression. Those findings are consistent with the role of TNFα in the resolution of inflammation and might help to elucidate the complex development of autoimmune uveitis.
authors.affiliation: IRIBHM (Institute of Interdisciplinary Research), Université Libre De Bruxelles-Campus Erasme, Brussels, Belgium. mmakhoul@ulb.ac.be
authors.forename: Maya
authors.initials: M
authors.lastname: Makhoul
authors.forename: Catherine
authors.initials: C
authors.lastname: Bruyns
authors.forename: William's Elong
authors.initials: WE
authors.lastname: Edimo
authors.forename: Lia Judice
authors.initials: LJ
authors.lastname: Relvas
authors.forename: Magdalena
authors.initials: M
authors.lastname: Bazewicz
authors.forename: Philippe
authors.initials: P
authors.lastname: Koch
authors.forename: Laure
authors.initials: L
authors.lastname: Caspers
authors.forename: François
authors.initials: F
authors.lastname: Willermain
mesh_terms: D000911:Antibodies, Monoclonal / Q000494:pharmacology; D017209:Apoptosis; D015153:Blotting, Western; D002478:Cells, Cultured; D005434:Flow Cytometry; D000949:Histocompatibility Antigens Class II / Q000378:metabolism*; D006801:Humans; D047468:Immunoprecipitation; D000069285:Infliximab; D018799:Intercellular Adhesion Molecule-1 / Q000378:metabolism; D050856:Interferon Regulatory Factor-1 / Q000378:metabolism; D007371:Interferon-gamma / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D060888:Real-Time Polymerase Chain Reaction; D055213:Retinal Pigment Epithelium / Q000187:drug effects* / Q000378:metabolism; D050794:STAT1 Transcription Factor / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
chemical_list: D000911:Antibodies, Monoclonal; D000949:Histocompatibility Antigens Class II; D050856:Interferon Regulatory Factor-1; D050794:STAT1 Transcription Factor; C494079:STAT1 protein, human; D014409:Tumor Necrosis Factor-alpha; D018799:Intercellular Adhesion Molecule-1; D007371:Interferon-gamma; D000069285:Infliximab