Immunosuppressive properties of tissues of the ocular anterior segment

Analysis of primed donor-specific T cells in recipient mice bearing orthotopic corneal allografts

BACKGROUND

Orthotopic corneal allografts placed in normal eyes of mice are often not rejected, whereas grafts placed in high-risk (neovascularized) eyes are routinely destroyed. Because rejection of solid tissue allografts is usually mediated by donor-specific T cells, we wished to determine the extent to which donor-specific T cells become primed in mice bearing orthotopic corneal allografts in normal and "high-risk" eyes.

METHODS AND RESULTS

Our data indicate corneal allografts placed in neovascularized eyes were rejected within 2 weeks, and lymph nodes draining these grafts contained primed donor-specific T cells that proliferated in vitro and displayed cytotoxic activity. By contrast, only 50% of corneal allografts placed in normal eyes experienced rejection. Lymphoid cells from all of these mice displayed donor-specific proliferative activity, irrespective of whether the graft was accepted or rejected. At no time were donor-specific cytotoxic T cells detected. Failure to detect primed cytotoxic T cells was not the result of anergy or deletion of unprimed donor-specific precursors of CTL.

CONCLUSIONS

We conclude that primed donor-specific proliferative and cytotoxic T cells directed at MHC alloantigens correlate well with rejection of orthotopic corneal allografts in neovascularized high-risk eyes. However, rejection of cornea allografts in normal eyes does not correlate well with proliferative T cells, nor are donor MHC-specific cytotoxic T cells detected. The possibility is discussed that graft rejection in normal eyes is not mediated by T cells that recognize MHC alloantigens via the direct pathway, but via T cells that recognize donor alloantigens presented by recipient MHC molecules (indirect pathway).

Allergic and immunologic disorders of the eye. Part I: immunology of the eye

Immuno-ophthalmology evolved during the 20th century as a subspecialty linking ophthalmologists and immunologists. This emerging subspecialty has focused on the use of immunology to better understand and treat ocular disorders. To help the allergist/clinical immunologist better appreciate the growing field of immuno-ophthalmology, this 2-part review series (Part II: Ocular Allergy will appear in the December issue of the Journal) will provide an overview of the impact that immunology has had on our understanding and treatment of allergic and immunologic eye diseases. The current review will focus on mechanisms by which mast cells, T cells, eosinophils, cytokines, and other inflammatory constituents contribute to the unique features of eye disease and their link to allergic responses that occur in other organs of the body.

Detection and immunolocalization of macrophage migration inhibitory factor in rat iris and ciliary epithelium

To elucidate the role of macrophage migration inhibitory factor (MIF) in ocular inflammation, we examined the localization of MIF in the normal anterior uveal tract of rats. Immunohistochemistry using an anti-MIF antibody revealed that MIF was present in non-pigment epithelial cells of the ciliary body and the epithelial cells of the iris. Western blot analysis of these tissues showed a single band specific for MIF protein. The expression of MIF mRNA in these tissues was further confirmed by reverse transcription-polymerase chain reaction. Since MIF is known to be a potent proinflammatory cytokine, identification of the protein in iris and ciliary epithelial cells suggests the possibility that it may play an important role in ocular inflammation.