AIM: To explore the mechanism of rejection of bioengineered keratoplasty by the laser confocal microscope and immunopathological studies.

METHODS: Retrospective case study. Five patients(5 eyes)who underwent bioengineered keratoplasty for infectious keratitis from Sep.2018 to Dec.2020 and were immunologically rejected included. All observers were monocular. Slit-lamp was used to examine corneal transparency and corneal neovascularization. The cornea was dynamically observed under laser confocal microscopy, the density of subepithelial langerhans cells and stromal inflammatory cells was recorded after graft rejection, and the contralateral eye was used as the control group for statistical analysis. The infiltration and distribution of CD4⁺ cells, CD8⁺ cells and inflammatory cells were observed after immunohistochemical staining of bioengineered corneas during corneal allograft.

RESULTS: Confocal laser microscopy showed that a large number of langerhans cells were activated under the corneal epithelium of the intraoperative eye, and the activation ratio was significantly different from that of the contralateral eye(χ²=38.29, P<0.001). The stromal layer was rich in inflammatory cells, which was significantly different from that of the contralateral eye(t=32.5, P<0.05). Immunohistochemical staining and HE staining were performed on the bioengineering corneal tissue. CD4⁺ and CD8⁺ cells were observed in all corneal stromal layers, and only one case had a large number of eosinophils.

CONCLUSION: Immunopathology of rejection after bioengineered keratoplasty confirmed that T-cell-mediated cellular immunity plays an important role in the pathogenesis, and hypersensitivity to xenoantigen may be involved in it.