Tear and conjunctival changes during the allergen-induced early- and late-phase responses

Background: Allergic eye disease is common, but little is known about the u nderlying disease mechanisms. Conjunctival allergen challenge causes sympto ms similar to those of seasonal allergic conjunctivitis and is a useful mod el to study. Objective: We have used allergen challenge to investigate the course of the ocular response, tear inflammatory mediators, tissue adhesion protein expr ession, and cellular infiltration. Methods: Eighteen atopic patients and 4 nonatopic control subjects were cha llenged with extracted mixed grass or Dermatophagoides pteronyssinus in one eye and control vehicle in the other. The clinical response was recorded, and tears mere collected over a 6-hour period. Conjunctival biopsy specimen s mere taken from the challenged eye at 6 or 24 hours. Results: An early-phase response (maximal at 20 minutes) showed a significa nt increase in tear histamine and tryptase levels, reducing to control leve ls again by 40 minutes. At 6 hours, a late-phase response occurred with inc reased symptoms, a second peak of tear histamine and eosinophil cationic pr otein but not tryptase, upregulation of the adhesion molecules E-selectin a nd intercellular adhesion molecule, and a cellular infiltrate of mast cells , neutrophils, eosinophils, macrophages, and basophils, with T cells increa sed only in bulbar biopsy specimens. Conclusions: The early peaks of tear histamine plus tryptase indicate that the mast cell is responsible for the early-phase response, but basophils ma y be involved in the late-phase response. Both tear and biopsy findings und erline the significance of the late-phase response as the transition betwee n a type I response and clinical disease.