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Hiroko Taniguchi, Hidenori Hase, Hisaya Akiba, Hideo Yagita, Miyuki Azuma, Junko Hori; Expression of TLT-2 in Corneal Tissue and Macrophages after Corneal Transplantation and Association With Immune Privilege of Corneal Allografts. Invest. Ophthalmol. Vis. Sci. 2011;52(14):1143.
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B7-H3 belongs to the B7 superfamily, a group of molecules that costimulate or down-modulate T-cell responses. We have previously reported that B7-H3 is an essential molecule for acceptance of corneal allografts and induction of allo-specific anterior chamber-associated immune deviation (ACAID). Recently, triggering receptor expressed on myeloid cells-like transcript-2 (TLT-2) has been identified as a B7-H3 receptor. The purpose of the present study is to investigate expression of TLT-2 in the ocular tissue and immune cells, and to elucidate its role on the immune privilege of corneal allografts.
Normal corneas of C57BL/6 were transplanted orthotopically into the normal eyes of BALB/c mice. Expression of TLT-2 in normal and in graft-bearing eyes was evaluated by RT-PCR and immunohistochemically by confocal microscopy. In different sets of recipients, anti-TLT-2 monoclonal antibody (mAb) or control rat IgG were administered intraperitoneally, and allograft survival was compared.
RT-PCR and immunohistochemical studies revealed that there was no expression of TLT-2 in the normal eye. On the other hand, TLT-2 was expressed in the corneal endothelium and epithelium in the allografts. These corneal allografts were infiltrated with TLT-2+CD11b+ cells. In the recipients treated with anti-TLT-2 mAb, all allografts were rejected. The survival of these allografts was significantly shortened in comparison with that of the control group (p<0.05).
TLT-2 is not expressed in normal ocular tissue, but its expression is up-regulated both in corneal tissue and on macrophages after corneal allo-transplantation. TLT-2 plays a suppressive role in immune response of corneal allografts. TLT-2 expressed in ocular tissue and macrophages within the cornea may contribute to allograft acceptance.
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