OBJECTIVETo gain insight into the role of Toll-like receptor 2 (TLR2) in graft rejection following penetrating keratoplasty, and investigate the expression of TLR2 mRNA in the corneal graft.

METHODSPenetrating keratoplasty was performed in 3 groups of rats for orthotopic autologous corneal transplantation (group A), allograft corneal transplantation (group B), or allograft corneal transplantation with hormone treatment (C). The transparency and neovascularization of the cornea were observed using a slit-lamp microscope and scored according to the rejection index, with normal cornea serving as the control. The corneal tissues were sampled at 5, 7, and 9 days after the transplantation for histopathological examination and detection of TLR2 mRNA expression using RT-PCR.

RESULTSWith the passage of time, edema, opacities and neovascularization of the corneal graft occurred after the operation in all the groups. Seven days after the operation, the rejection index of group B, but not that of groups A and C, met the diagnostic criteria for graft rejection with also support by histopathological evidence. The expression of TLR2 mRNA was detected in normal corneas and augmented in the corneal grafts in the 3 transplantation groups. TLR2 mRNA expression in group B was significantly higher than that of group A, and the expression in group C decreased significantly in comparison with that in group B (P<0.05).

CONCLUSIONAs the recognition receptors of native immune system, TLR2 in the rejected corneal grafts may recognize the allograft antigen and play a role in acute graft rejection after penetrating keratoplasty.