Tim-3/Galectin-9 Pathway-Mediated Protection of Corneal Endothelial Cells From Killing by Allo-Reactive-T Cells

Abstract

Purpose: : T cell immunoglobulin and mucin domain (Tim)-3 is a regulatory molecule of T cell function. Galectin-9 is a Tim-3 ligand. We have demonstrated that Galectin-9 is constitutively expressed on corneal endothelium and the iris-ciliary body and Tim-3/Galectin-9 pathway plays an immunosuppressive role in corneal allografts, but is not associated with induction of anterior chamber-associated immune deviation (ACAID). To further investigate the mechanisms Tim-3/Galectin-9 pathway associated immune suppression, we examined destruction of corneal endothelial cells (CECs) by allo-reactive T cells in vitro.

Methods: : Corneas from C57BL/6 (B6) eyes pre-treated with anti-Galectin-9 mAb or control rat IgG were incubated with CD4+ T cells for 6 h. CD4+ T cells were purified from the spleen of BALB/c mice that were presensitized by subcutaneous immunization with allo (B6) splenocytes or with third-party (C3H/He) splenocytes, or from the spleen of naive BALB/c, B6 or C3H/He mice. Dead CECs stained with propidium iodide were counted and compared.

Results: : The number of dead CECs in anti-Galectin-9 mAb-treated corneas was significantly larger than that in control IgG-treated corneas after incubation with allo-reactive T cells. In contrast, no significant differences were observed between anti-Galectin-9 mAb and control IgG-treated corneas with naive BALB/c or C3H/He T cells, and activated T cells against third-party allo-antigens.

Conclusions: : Gal-9 expressed on CECs plays a role in protecting CECs from destruction by allo-reactive CD4+ T cells.

Keywords: immune tolerance/privilege • transplantation