Human corneal endothelial cells expressing programmed death-ligand 1 (PD-L1) suppress PD-1+ T helper 1 cells by a contact-dependent mechanism.
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.
Sugita
Sunao
S
Department of Ophthalmology & Visual Science, Tokyo Medical and Dental University Graduate School of Medicine, Tokyo, Japan. sunaoph@tmd.ac.jp
Usui
Yoshihiko
Y
Horie
Shintaro
S
Futagami
Yuri
Y
Yamada
Yukiko
Y
Ma
Juan
J
Kezuka
Takeshi
T
Hamada
Hirofumi
H
Usui
Tomohiko
T
Mochizuki
Manabu
M
Yamagami
Satoru
S
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
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