Immunology and immunomodulation of corneal transplantation.

Corneal allografts are the oldest, most common, and most successful transplants performed on humans and animals. The cornea is endowed with a constellation of unique factors that contribute to its immune privilege and the low incidence of immune rejection. In spite of this immune privilege, 10 percent of first-time corneal grafts will undergo immune rejection. Several novel therapeutic strategies hold promise for modulating the alloimmune response by either promoting antigen-specific tolerance or redirecting the host's response from a Th1 pathway toward a Th2 pathway.