ABSTRACT
Corneal transplantation is the most common and, arguably, the most successful form of solid tissue transplantation. In the United States alone, over 33,000 corneal transplants are performed each year (1). In uncomplicated cases, 90% acceptance is commonplace even though tissue typing and administration of systemic immunosuppressive drugs are not employed. Such success is unparalleled in other forms of transplantation and has led to the proposition that corneal allografts enjoy immune privilege (2-5). A panoply of anatomic, physiologic, and immunoregulatory parameters contribute to the immune privilege of corneal allografts (Table 1). These parameters can be reduced to three broad categories: (i) those that block induction of alloimmunity; (ii) those that divert or suppress alloimmune responses; and (iii) those that inhibit the host’s immune effector elements.
