title: Human corneal endothelial cells expressing programmed death-ligand 1 (PD-L1) suppress PD-1+ T helper 1 cells by a contact-dependent mechanism.
abstract: OBJECTIVE
  This study was designed to determine whether human corneal endothelial (HCE) cells could regulate the activation of bystander T cells in vitro.
  
  
  METHODS
  HCE cell lines were established from primary HCE cells. Target-activated T cells were used allogeneic T cells and Jurkat T-cell lines. As an additional target, T-cell clones from uveitis patients were established from aqueous humor via a limiting dilution. T-cell activation was assessed for proliferation by [(3)H]-thymidine incorporation, carboxyfluorescein succinimidyl ester incorporation, or IFNgamma production. Expression of co-stimulatory molecules on IFNgamma-treated corneal endothelial and non-treated cells was evaluated by flow cytometry, RT-PCR, or immunohistochemistry. Expression of co-stimulatory receptors on target T cells was evaluated by flow cytometry. Blocking antibodies was used to abolish the HCE-inhibitory function.
  
  
  RESULTS
  HCE cells suppressed both in vitro proliferation and IFNgamma production by CD4(+) T cells via a cell contact-dependent mechanism. HCE constitutively expressed co-stimulatory molecules programmed death-ligand 1 (PD-L1) and PD-L2, and their expression was enhanced by IFNgamma. HCE efficiently inhibited the proliferation of Th1 cells that overexpressed PD-1 among various activated T-cell lines and clones established from patients with uveitis or corneal endotheliitis. A neutralizing mAb for PD-L1, but not PD-L2, blocked the suppressive effect of HCE on Th1 cells.
  
  
  CONCLUSIONS
  HCE can impair the effector functions and activation of Th1 infiltrating CD4(+) T cells via the PD-1/PD-L1 interaction. The data support the hypothesis that corneal endothelium may contribute to maintenance of the privileged immune status of the anterior chamber of the eye by inducing peripheral immune tolerance.
authors.affiliation: Department of Ophthalmology & Visual Science, Tokyo Medical and Dental University Graduate School of Medicine, Tokyo, Japan. sunaoph@tmd.ac.jp
authors.forename: Sunao
authors.initials: S
authors.lastname: Sugita
authors.forename: Yoshihiko
authors.initials: Y
authors.lastname: Usui
authors.forename: Shintaro
authors.initials: S
authors.lastname: Horie
authors.forename: Yuri
authors.initials: Y
authors.lastname: Futagami
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Yamada
authors.forename: Juan
authors.initials: J
authors.lastname: Ma
authors.forename: Takeshi
authors.initials: T
authors.lastname: Kezuka
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Hamada
authors.forename: Tomohiko
authors.initials: T
authors.lastname: Usui
authors.forename: Manabu
authors.initials: M
authors.lastname: Mochizuki
authors.forename: Satoru
authors.initials: S
authors.lastname: Yamagami
mesh_terms: D015703:Antigens, CD / Q000378:metabolism*; D017209:Apoptosis / Q000502:physiology; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism*; D018122:B7-1 Antigen / Q000378:metabolism; D060890:B7-H1 Antigen; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D002450:Cell Communication / Q000502:physiology*; D002460:Cell Line; D049109:Cell Proliferation; D004728:Endothelium, Corneal / Q000502:physiology*; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D005452:Fluoresceins / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D007371:Interferon-gamma / Q000378:metabolism; D008213:Lymphocyte Activation; D061026:Programmed Cell Death 1 Receptor; D020133:Reverse Transcriptase Polymerase Chain Reaction; D018417:Th1 Cells / Q000276:immunology*; D013936:Thymidine / Q000378:metabolism
chemical_list: D015703:Antigens, CD; D051017:Apoptosis Regulatory Proteins; D018122:B7-1 Antigen; D060890:B7-H1 Antigen; C423236:CD274 protein, human; D005452:Fluoresceins; C105992:PDCD1 protein, human; D061026:Programmed Cell Death 1 Receptor; C027780:carboxyfluoresceindiacetate; D007371:Interferon-gamma; D013936:Thymidine