GITR ligand-mediated local expansion of regulatory T cells and immune privilege of corneal allografts.
OBJECTIVE
The pathway between the glucocorticoid-induced tumor necrosis factor receptor family-related protein (GITR) and GITR ligand (GITRL) has been shown to control the function of regulatory T cells (Treg). The present study was conducted to investigate the role of this pathway and Treg in establishing immune privilege status for corneal allografts.


METHODS
Corneas of C57BL/6 mice were orthotopically transplanted into the eyes of BALB/c mice, and graft survival was assessed. A separate set of BALB/c mice received an anterior chamber injection of C57BL/6 splenocytes, and induction of allo-specific anterior chamber-associated immune deviation was assessed. Recipients were intraperitoneally administrated anti-GITRL, anti-CD25 monoclonal antibodies (mAb), or control immunoglobulin (IgG). Expressions of GITRL, GITR, and Foxp3 in the allografts were assessed. In vitro, cornea pretreated with anti-GITRL mAb or control IgG was incubated with T cells, and destruction of corneal endothelial cells and the population of Foxp3(+)CD25(+)CD4(+) T cells were assessed.


RESULTS
GITRL was expressed constitutively in the cornea and iris-ciliary body. GITRL-expressing allografts were infiltrated with Foxp3+GITR+CD25+CD4(+) T cells. Blockade of GITRL did not affect allo-specific ACAID but led to infiltration of Foxp3(-)CD4(+) T cells and allograft rejection. Depletion of CD25+CD4(+) Treg also accelerated allograft rejection. Destruction of corneal endothelial cells by T cells was significantly enhanced in GITRL-blocked cornea compared with control cornea. Foxp3+CD25+CD4(+) T cells were increased after incubation with GITRL-expressing cornea, but not with GITRL-blocked cornea.


CONCLUSIONS
Presence of Foxp3+CD25+CD4(+) Treg in the allograft is necessary for allograft survival. GITRL-dependent expansion of Treg within the cornea is one mechanism underlying immune privilege in corneal allografts.
Hori
Junko
J
Department of Ophthalmology, Nippon Medical School, Tokyo, Japan. jhori-tky@umin.ac.jp
Taniguchi
Hiroko
H
Wang
Mingcong
M
Oshima
Masamichi
M
Azuma
Miyuki
M
D000818:Animals; D000867:Anterior Chamber / Q000276:immunology; D003315:Cornea / Q000276:immunology*; D016039:Corneal Transplantation; D005434:Flow Cytometry; D019084:Fluorescent Antibody Technique, Indirect; D051858:Forkhead Transcription Factors / Q000276:immunology; D053450:Glucocorticoid-Induced TNFR-Related Protein; D006085:Graft Survival / Q000276:immunology*; D053645:Interleukin-2 Receptor alpha Subunit / Q000276:immunology; D008024:Ligands; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D012333:RNA, Messenger / Q000235:genetics; D017475:Receptors, Nerve Growth Factor / Q000502:physiology*; D018124:Receptors, Tumor Necrosis Factor / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013154:Spleen; D050378:T-Lymphocytes, Regulatory / Q000276:immunology*; D014184:Transplantation, Homologous; D048069:Tumor Necrosis Factors / Q000502:physiology*
D051858:Forkhead Transcription Factors; C498833:Foxp3 protein, mouse; D053450:Glucocorticoid-Induced TNFR-Related Protein; C508018:Il2ra protein, mouse; D053645:Interleukin-2 Receptor alpha Subunit; D008024:Ligands; D012333:RNA, Messenger; D017475:Receptors, Nerve Growth Factor; D018124:Receptors, Tumor Necrosis Factor; C106544:Tnfrsf18 protein, mouse; C478966:Tnfsf18 protein, mouse; D048069:Tumor Necrosis Factors