title: Role of human corneal endothelial cells in T-cell-mediated alloimmune attack in vitro.
abstract: OBJECTIVE
  Human corneal endothelial cells (HCEC) are a potential target of immune attack after corneal transplantation. The aim of this in vitro study was to investigate the role of HCEC during the alloimmune response of T-cells by examining cytokine profiles, function of the immunosuppressive enzyme indoleamine 2,3-dioxigenase (IDO), major histocompatibility complex (MHC-I/-II), T-cell proliferation, and the induction of cell death.
  
  
  METHODS
  Real-time PCR and RP-HPLC were used to determine IDO expression and activity. Multiplex assay was performed for quantification of cytokine levels. T-cell proliferation was assessed by thymidine incorporation, and HCEC cell death was measured by flow cytometry.
  
  
  RESULTS
  Human corneal endothelial cells induce strong proliferation of allogeneic T-cells and an increase of proinflammatory cytokines such as interleukin-1α (IL-1α), IL-1β, IL-6, interferon-gamma (IFN-γ), and tumor necrosis factor-alpha (TNF-α). Tumor necrosis factor-alpha (and to a lesser extent IFN-γ) induces apoptosis. Moreover, IFN-γ strongly upregulates MHC-II molecules and IDO activity in HCEC as reflected by high kynurenine (Kyn) concentrations. Interestingly, the T-cell response was not affected by increased IDO activity, since blocking of IDO did not affect the proliferation rate. Indoleamine 2,3-dioxigenase-induced Kyn levels did not exceed concentrations of 175 ± 20 μM. Concentrations of ≥400 μM Kyn were required to suppress T-cell proliferation.
  
  
  CONCLUSIONS
  Our data show that T-cell attack on HCEC leads to increased concentrations of proinflammatory cytokines. Inflammatory cytokines induce apoptosis and upregulate MHC-II molecules and IDO in HCEC. Although increased IDO activity does not influence the T-cell response, it constitutes an inflammatory marker of the alloimmune response toward HCEC.
authors.affiliation: University Hospital Heidelberg, Department of Immunology, Heidelberg, Germany.
authors.forename: Imad
authors.initials: I
authors.lastname: Lahdou
authors.forename: Christoph
authors.initials: C
authors.lastname: Engler
authors.forename: Stefan
authors.initials: S
authors.lastname: Mehrle
authors.forename: Volker
authors.initials: V
authors.lastname: Daniel
authors.forename: Mahmoud
authors.initials: M
authors.lastname: Sadeghi
authors.forename: Gerhard
authors.initials: G
authors.lastname: Opelz
authors.forename: Peter
authors.initials: P
authors.lastname: Terness
mesh_terms: D001327:Autoimmune Diseases / Q000235:genetics / Q000276:immunology* / Q000473:pathology; D015551:Autoimmunity; D016923:Cell Death; D002460:Cell Line; D049109:Cell Proliferation; D016039:Corneal Transplantation; D004247:DNA / Q000235:genetics; D004728:Endothelium, Corneal / Q000276:immunology* / Q000378:metabolism / Q000473:pathology; D005786:Gene Expression Regulation; D006084:Graft Rejection / Q000235:genetics / Q000276:immunology* / Q000473:pathology; D006801:Humans; D007111:Immunity, Cellular / Q000276:immunology*; D050503:Indoleamine-Pyrrole 2,3,-Dioxygenase / Q000096:biosynthesis / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D013601:T-Lymphocytes / Q000276:immunology* / Q000473:pathology
chemical_list: D050503:Indoleamine-Pyrrole 2,3,-Dioxygenase; D004247:DNA
keywords: IDO; alloimmune response; cell death; human corneal endothelial cells