Immunosuppresive Therapy in Ocular Surface Transplantation

Abstract

Patients with bilateral limbal stem cell deficiency who are not candidates for autologous transplantation generally require allograft tissue to restore the stem cell population.1 Compared to conventional penetrating keratoplasty, limbal allografts are at significantly higher risk for rejection. This increased susceptibility to rejection is primarily because of the vascularity of the limbal area, which allows greater access for the immune system. It is also due to the greater antigenicity of the limbal tissue, which contains a significant number of Langerhans cells.2 Previous studies have demonstrated the importance of immunosuppression in maintaining graft survival following limbal stem cell transplantation.3–6 Our experience with the keratolimbal allograft (KLAL) procedure in 54 cases further underscored the need for oral immunosuppression.7 Specifically, among the 28 cases who received oral cyclosporin A (CsA) for 18 months, 24 eyes (87%) achieved a stable ocular surface compared with 16 of 26 cases (62%) who did not get oral CsA (p 0.05). This and other reports suggest that achieving adequate immunosuppression after KLAL requires oral medications, and that topical therapy alone is insufficient for long-term graft survival. It should be emphasized that immunosuppression is necessary in all patients who receive limbal allografts, even in those who receive HLA-matched living-related tissue.8 The use of oral immunosuppressive agents requires careful monitoring and knowledge of the potential side effects. The side effects and adverse reactions due to these medications are the main potential cause of morbidity associated with limbal allograft transplantation. In this chapter, we will review the basic mechanism of rejection and the various topical and oral immunosuppressive regimens available for patients who undergo limbal allograft transplantation. Mechanism of Rejection