Lack of T6 induction on human corneal Langerhans cells in vitro.

Previous studies have shown that Langerhans cells (LC) in normal human corneas differ from their counterparts in other epithelia (eg, skin, gingival, cervical) by their lack of the thymocyte antigen T6 on their membranes. In those studies only three out of four very young infant corneas (newborn, 3-day-, 8-day-old) have displayed positive T6 staining to date. Corneas from older infants and adults have demonstrated no such staining. This study tested the capacity of corneal LC to express T6 by in vitro induction with several immunomodulating agents. Human gamma interferon (IFN gamma was tested at 1000 U/ml, 500 U/ml and 100 U/ml. Interleukin-1 (IL-1) was tested at 100 U/ml, 50 U/ml and 20 U/ml. Thymopoietin pentapeptide (TP-5) was tested at 10 micrograms/ml, 1 micrograms/ml and 0.1 microgram/ml. Combinations of these agents were also tested in a similar fashion. None of these immunomodulating agents or combinations of them were able to induce T6 expression on normal corneal LC. This may reflect an innate incapacity of these cells to express this antigen or dosage requirements in excess of those tested.