Corneal tissue may be transplanted successfully because the cornea occupies which type of site?

• A. The cornea is nonantigenic
• B. Corneal antigens do not activate T cells
• C. Anticorneal antibodies are easily suppressed
• D. The cornea occupies a privileged site not usually seen by the immune system

Answer: (D)

The key idea is immune privilege. The cornea sits in an environment of immune tolerance within the eye, so transplanted corneal tissue can survive with a much lower risk of rejection. This privilege comes from its avascular and alymphatic nature, which limits the movement of donor antigens to regional lymph nodes where T cells would normally be activated. The aqueous humor also contains immunosuppressive factors that further dampen immune responses, and exposure to corneal antigens in the eye can trigger ACAID (an anterior chamber–associated immune deviation) that promotes systemic tolerance rather than inflammation. So the cornea is transplanted successfully because it occupies an immune-privileged site not usually seen by the robust immune system.