Effect of donor Langerhans cells on corneal graft rejection

Unlike other cutaneous surfaces, the central portion of the corneal epithelium is typically devoid of Langerhans cells. The absence of Ia+ Langerhans cells in the central cornea is of more than casual interest and may explain the immunologic privilege that is characteristic of corneal allografts. The present communication summarizes previous studies that examined the role of corneal Langerhans cells in eliciting alloimmune responses and corneal graft rejection in rodents. Under normal circumstances, corneal allografts are poorly immunogenic when residing in the avascular ocular graft bed even though the graft displays large quantities of alloantigens. The afferent blockade of the immune response can be circumvented by donor-derived Langerhans cells that serve as potent immunogens for all categories of corneal allografts except grafts involving allodisparity only at class I major histocompatibility complex loci. Thus, the presence of donor-derived Langerhans cells exerts profound effects on the fate of corneal allografts.