Despite the existence of ocular immune privilege, immune rejection may be a barrier to successful retinal transplantation. We have examined in mice the extent to which the subretinal space (SRS) is an immune privileged site, and whether retinal pigment epithelium and neuronal retinal tissue have properties of immune privileged tissues. We report that (1) The SRS is an immune privileged site; (2) Neonatal RPE is an immune privileged tissue; (3) Neuronal retina is a partially immune privileged tissue; and (4) Microglia within neonatal neural retina grafts promote photoreceptor differentiation, become activated, and induce sensitization of the recipient and serve as targets of immune rejection.
CN is a common phenomenon after non-high-risk keratoplasty. New vessels rarely reach the host-graft junction, most commonly develop from the 6 o'clock and 12 o'clock positions and are usually located between epithelium and Bowman's layer (i.e., at the level of the superficial suture). The direction of vessel growth from the limbus towards the outer suture ends suggests release of angiogenic factors in this area. Prolongation of topical steroid therapy after non-high-risk keratoplasty beyond 6 months in this study did not significantly influence incidence and extent of CN, corneal endothelial cell count, aqueous flare values and best-corrected visual acuity observed 1 year after keratoplasty.
The incidence of episodes of corneal endothelial allograft rejection following normal-risk keratoplasty was 13.5% within the first two postoperative years. However, the frequency of irreversible immunologic graft failure (3 per thousand) was lower than reported in the literature. Patients should be regularly followed up for at least 18 months postoperatively. Patients with underlying atopic dermatitis or dry eyes should receive special ophthalmological care.
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