B7+ iris pigment epithelial cells convert T cells into CTLA-4+, B7-expressing CD8+ regulatory T cells.
OBJECTIVE
To determine whether iris PE (IPE) promotes the generation of regulatory T-cells (Tregs) with cell contact via B7-2/CTLA-4 interactions.


METHODS
T cells were cocultured with IPE cells obtained from eyes of normal and B7-deficient mice, x-irradiated, and used as regulators. IPE T regulator cells (IPE Tregs) of normal and CD28- or CTLA-4-deficient mice were established. Target bystander T cells were established from normal splenic T cells with anti-CD3 antibodies. T-cell activation was assessed for proliferation by [3H]-thymidine incorporation. Neutralizing anti-B7-1 and/or B7-2 antibodies, anti-CTLA-4 antibodies, CTLA-4-Ig fusion proteins were used to abolish regulatory function. IPE-exposed CD8+ T cells were evaluated for expression of B7, CTLA-4, and Foxp3 by using RT-PCR and flow cytometry. CD8+ IPE Tregs were depleted of B7-2+ and CTLA-4+ T cells and assayed for suppressive activity by adding them to bystander T cells.


RESULTS
T cells acquired T regulatory activity when exposed to cultured IPE. Ciliary body PE cells did not promote conversion of T cells into Tregs. IPE converted CD8+, but not CD4+, T cells into Tregs by direct cell contact. In the conversion, IPE and responding T cells must both express endogenously synthesized B7-1 and B7-2, and the T cells must also express CTLA-4. Expression of CD28 molecules was not necessary for Treg generation. In addition, the CD8+ Tregs that fully suppress activation of bystander T cells expressed Foxp3.


CONCLUSIONS
IPE cells promote conversion of T cells into Tregs solely through a contact-dependent mechanism. T cells exposed to IPE cells acquire full regulatory capacity.
Sugita
Sunao
S
Schepens Eye Research Institute, Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts 02114, USA.
Keino
Hiroshi
H
Futagami
Yuri
Y
Takase
Hiroshi
H
Mochizuki
Manabu
M
Stein-Streilein
Joan
J
Streilein
J Wayne
JW
D000818:Animals; D015703:Antigens, CD / Q000276:immunology*; D000943:Antigens, Differentiation / Q000276:immunology* / Q000502:physiology; D051940:B7-2 Antigen / Q000276:immunology*; D017252:CD3 Complex / Q000276:immunology; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology*; D060908:CTLA-4 Antigen; D002455:Cell Division; D002478:Cells, Cultured; D018920:Coculture Techniques; D005434:Flow Cytometry; D051858:Forkhead Transcription Factors / Q000235:genetics / Q000276:immunology; D007498:Iris / Q000166:cytology*; D008213:Lymphocyte Activation / Q000276:immunology*; D008212:Lymphocyte Depletion; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D010857:Pigment Epithelium of Eye / Q000276:immunology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D050378:T-Lymphocytes, Regulatory / Q000276:immunology*
D015703:Antigens, CD; D000943:Antigens, Differentiation; D051940:B7-2 Antigen; D017252:CD3 Complex; D060908:CTLA-4 Antigen; C497965:Cd86 protein, mouse; C556707:Ctla4 protein, mouse; D051858:Forkhead Transcription Factors; C498833:Foxp3 protein, mouse