Corneal allograft rejection.

Corneal allograft rejection remains the major impediment to the success of the most commonly performed solid tissue transplant. Immunologic mechanisms, particularly cellular immunity, appear to be responsible for the majority of cases of graft failure. While the prognosis for dystrophic and noninflammatory conditions is highly favorable, the failure rate in vascularized corneas can be as high as 60%. Considerable interest in the HLA system has led to a greater understanding of the distributions of these major histocompatibility antigens in the cornea. It is generally believed that tissue typing and matching class I and class II HLA antigens will result in a higher success rate for corneal transplantation. Other strategies for reducing graft-host disparity, such as decreasing the antigen load, interfering with clonal expansion, and utilizing new forms of immunotherapy, will undoubtedly contribute to better survival of corneal transplants.