THE IMMUNOLOGY OF CORNEAL GRAFT-REJECTION

Corneal transplantation is the most successful of organ transplants du e to the fact that the eye is an immunologically privileged site, and the cornea is an immunologically privileged tissue. The factors respon sible for this include presence of the blood-aqueous barrier, the avas cularity of the cornea, the absence of classic antigen-presenting cell s (APCs) in the central cornea, inhibitory factors in the aqueous humo r, the phenomenon known as anterior chamber-associated immune deviatio n (ACAID), and the intraocular expression of Fas ligand. Loss of ocula r immune privilege can occur with breaching of the blood-ocular barrie r, corneal neovascularization, migration of classic APCs to the center of the cornea, loss of inhibitory factors in aqueous humor, abrogatio n of ACAID, and loss of Fas ligand expression within the anterior cham ber. The purpose of this review is to analyze these events and how the y relate to corneal graft rejection. A discussion on future research a nd therapeutic modalities is provided.