Therapeutic considerations: symptoms, cells and mediators.

Abstract

Immuno-histopathological studies of conjunctival tissue biopsied from patients with non-sight-threatening allergic conjunctivitis or with sight-threatening allergic keratoconjunctivitis should lead to more effective management of these eye conditions, based on the specific cellular involvement. The major difference between these two categories of eye disease was the occurrence of T-lymphocytes, which were absent in the former but prominent in the sight-threatening disorders. Seasonal and perennial allergic conjunctivitis both showed a heavy mast cell increase, due to infiltration of mucosal type mast cells, and allergen challenge studies linked mast cell histamine release to the early phase reaction occurring within 20 minutes. A second histamine peak at six hours after challenge might implicate basophils (or refractory mast cells) and was accompanied by a rise in eosinophil cationic protein. In sight-threatening, chronic allergic keratoconjunctivitis the responses were clearly directed by T-cells, themselves the primary effector cell in atopic keratoconjunctivitis, whereas vernal keratoconjunctivitis displayed a T-cell driven eosinophilia, with increased expression of the adhesion molecules involved in tissue invasion by these cells. Appropriate therapies for each different category of conjunctivitis should be based on the specific immunopathology, and directed at the activated cell types that are primarily responsible for the disease process.