RETHINKING IMMUNOLOGICAL PRIVILEGE - IMPLICATIONS FOR CORNEAL AND LIMBAL STEM-CELL TRANSPLANTATION

Immunological privilege operates within the normal eye by multiple pas sive and active mechanisms, including antigen sequestration, maintenan ce of an immunosuppressive local environment and induction of apoptoti c death in infiltrating cells of the immune system, Ocular privilege m ight have developed to protect the eye from the collateral damage asso ciated with an inflammatory response to invading pathogens, Neverthele ss, corneal grafts do undergo irreversible immunological rejection and , furthermore, corneal graft rejection is very similar at a histologic al level to the rejection processes that operate in vascularized organ grafts. Ocular privilege is thus relative. The question arises as to how corneal grafts are rejected in the face of so many mechanisms desi gned to prevent immune responses from operating inside the eye - a que stion that is still essentially unanswered.