[Incidence and function of Langerhans cells in various corneal diseases]

Using immunohistochemical techniques, we investigated the distribution and frequency of Langerhans cells in corneal buttons obtained from patients who underwent corneal transplantation because of various corneal diseases. The frequency of these dendritic cells was similar to that in the normal epidermis in corneas with epidermalization after severe alkali burns. Numerous Langerhans cells, albeit in smaller numbers, were also present in the central corneal epithelium of patients with keratitis due to infection with herpes simplex virus, keratitis due to herpes zoster virus, bacterial corneal ulcers, corneal scars, corneal ulcers associated with rheumatoid arthritis, and patients with chronic corneal allograft reactions. The presence and persistence of Langerhans cells in diseased corneas may account for, at least in part, a breakdown of corneal immune privilege with a higher rate of rejection episodes after corneal transplantation. Furthermore, it is probable that Langerhans cells as potent antigen-presenting cells may also play an important role in the initiation and the progression of immune responses in various inflammatory corneal diseases.