Role of tumor necrosis factor receptor expression in anterior chamber-associated immune deviation (ACAID) and corneal allograft survival

PURPOSE: To determine the role of tumor necrosis factor receptors (TNFRs) in corneal allograft rejection. METHODS: Corneal epithelial and endothelial cells were examined by flow cytometry for the expression of TNFRI and TNFRII and their susceptibility to TNF-alpha-induced apoptosis. Corneal allografts from normal and TNFRI and TNFRII knockout (KO) C57BL/6 mice were transplanted to BALB/c hosts, and the fate of the allografts was monitored. C57BL/6 spleen cells were injected into the anterior chamber (AC) of BALB/c mice to induce anterior chamber-associated immune deviation (ACAID) and promote corneal allograft survival. The presence of ACAID suppressor cells in corneal allograft recipients was tested using a local adoptive transfer (LAT) assay. RESULTS: Murine corneal epithelial and endothelial cells expressed TNFRI and TNFRII and were susceptible to TNF-alpha-induced apoptosis, yet corneal allografts from either TNFRI or TNFRII donors did not enjoy a lower incidence of rejection or a prolongation in survival time compared to corneal allografts from normal C57BL/6 donors. Moreover, all 31 of the TNFRII KO corneal grafts were rejected by na?ve BALB/c hosts. Rejection of TNFRII KO corneal grafts occurred even though suppressor cells developed in the hosts and inhibited the expression of delayed-type hypersensitivity to donor alloantigens. CONCLUSIONS: Expression of TNFRII on corneal cells conveys a degree of protection against immune rejection of corneal allografts by a mechanism that is independent of ACAID. Moreover, induction of ACAID before the application of TNFRII KO corneal allografts fails to improve survival and does not replace the TNFRII-dependent protective mechanism.