Suppression of bystander T helper 1 cells by iris pigment epithelium-inducing regulatory T cells via negative costimulatory signals.
OBJECTIVE
To determine whether iris pigment epithelium (IPE)-induced T regulatory (Treg) cells can suppress the activation of bystander T cells with cell contact via costimulatory interactions.


METHODS
CD8(+) T cells were cocultured with IPE, x-irradiated, and then used as regulators (IPE-induced Treg cells). The target CD4(+) T cells from wild-type control or knockout donors were used for the assay. T-cell activation was assessed for proliferation by examining both [(3)H]-thymidine incorporation and cytokine production. Expression of costimulatory molecules on IPE-induced Treg cells was evaluated using RT-PCR, immunostaining, and flow cytometry. Expression of costimulatory receptors on target T cells or Treg cells was evaluated by flow cytometry. Neutralizing antibodies were then used to abolish regulatory function.


RESULTS
CD8(+) IPE-induced Treg cells significantly suppressed the activation of effector target T cells, e.g., T-cell proliferation and cytokine production such as Th1, Th2, and Th17 cytokines. Although IPE-induced Treg cells expressed various costimulatory molecules, including programmed cell death 1 ligand 1 (PD-L1), only PD-L1 on the Treg cells was actually delivered to target Th1 cells using cell-to-cell interaction (T-T interaction). If neutralizing antibodies for PD-L1 were cocultured with Treg cells, Th1 suppression was impaired. Moreover, Treg cells failed to suppress IFNgamma production by target CD4(+) T cells from programmed cell death 1 (PD-1) knockout donors. Th1-specific inhibition was exclusively achieved with direct cell contact.


CONCLUSIONS
T cells exposed to IPE in the eye that acquires full regulatory capacity express negative costimulators and suppress bystander Th1-type effector cells.
Sugita
Sunao
S
Department of Ophthalmology and Visual Science, Tokyo Medical and Dental University Graduate School, Tokyo, Japan. sunaoph@tmd.ac.jp
Horie
Shintaro
S
Yamada
Yukiko
Y
Keino
Hiroshi
H
Usui
Yoshihiko
Y
Takeuchi
Masaru
M
Mochizuki
Manabu
M
D000818:Animals; D019138:Antibodies, Blocking; D000954:Antigens, Surface / Q000378:metabolism; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism; D018122:B7-1 Antigen / Q000378:metabolism*; D060890:B7-H1 Antigen; D024201:Bystander Effect; D018920:Coculture Techniques; D016207:Cytokines / Q000096:biosynthesis; D005434:Flow Cytometry; D019084:Fluorescent Antibody Technique, Indirect; D007498:Iris / Q000166:cytology*; D008213:Lymphocyte Activation / Q000502:physiology*; D008562:Membrane Glycoproteins / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008822:Mice, Transgenic; D010455:Peptides / Q000378:metabolism*; D010857:Pigment Epithelium of Eye / Q000276:immunology*; D061026:Programmed Cell Death 1 Receptor; D020133:Reverse Transcriptase Polymerase Chain Reaction; D050378:T-Lymphocytes, Regulatory / Q000276:immunology*; D018417:Th1 Cells / Q000276:immunology*
D019138:Antibodies, Blocking; D000954:Antigens, Surface; D051017:Apoptosis Regulatory Proteins; D018122:B7-1 Antigen; D060890:B7-H1 Antigen; C498919:Cd274 protein, mouse; D016207:Cytokines; D008562:Membrane Glycoproteins; C491383:Pdcd1 protein, mouse; D010455:Peptides; D061026:Programmed Cell Death 1 Receptor