Prevention of the induction of allospecific cytotoxic T lymphocyte and delayed-type hypersensitivity responses by ultraviolet irradiation of corneal allografts

The effect of ultraviolet radiation (UVR) on the immunogenicity of corneal allografts was examined in a mouse model. Corneal allografts differing from the host at the entire MHC and multiple minor H loci were subjected to 200 mJ/cm² of UVB irradiation immediately prior to heterotopic transplantation. Analysis of cytotoxic T lymphocyte and delayed-type hypersensitivity responses revealed that UVR treated corneal grafts failed to induce either CTL or DTH responses in C57BL/6 recipients. UVB treatment abolished the immunogenicity of highly immunogenic corneal grafts containing either resident or infiltrating donor-specific Langerhans cells. Sequential grafting experiments demonstrated that UVB-treated grafts rendered the hosts anergic to subsequent immunization with highly immunogenic corneal limbus grafts that contained dense concentrations of Ia⁺Langerhans cells of donor origin. The results indicate that UV treatment not only reduces the immunogenicity of the corneal allograft but may also render it tolerogenic.