The role of conjunctival epithelial cells in chronic ocular allergic disease

Recent evidence suggests that mucosal epithelial cells are capable of activ ely participating in immune reactions via expression of surface antigens, s uch as adhesion molecules, and synthesis of cytokines. This appears to be i mportant in the pathophysiology of non-ocular allergic disorders. The objec tives of the experiments were to compare the expression of HLA-DR, ICAM-I a nd pro-allergic cytokines in conjunctival epithelial cells in the different chronic ocular allergic disorders with each other and with normal subjects . Conjunctiva from normal patients (n = 10) and patients with vernal keratoco njunctivitis (VKC, n = 10), atopic keratoconjunctivitis (AKC, n = 10) and c ontact lens-associated giant papilIary conjunctivitis (GPC, n = 10) were ex amined by immunohistochemistry. Epithelial cell staining for surface antige ns and cytokines was graded by one masked observer using a four point scale based on the percentage of epithelial cells staining positive. There was no expression of ICAM-I or HLA-DR in the normal conjunctival epit helial cells, but both antigens were induced on conjunctival epithelial cel ls in the allergic tissue, and there was greater expression in AKC and VKC compared with GPC. Cytokines IL-6, IL-8, RANTES and TNF-alpha all localised to normal conjunctival epithelial cells. RANTES was upregulated in all the allergic disorders and IL-8 was upregulated in GPC. IL-3 and GM-CSF were not expressed in normal conjunctival epithelial cells. GM-CSF was expressed in all disorders and there was greater expression in AKC compared with GPC and VKC. IL-3 was expressed only in AKC and VKC epith elial cells. These results suggest that conjunctival epithelial cells play an important pro-inflammatory role in chronic ocular allergic diseases; ICAM-1 may allow epithelial cells to recruit, retain and locally concentrate leukocytes; th e presence of HLA-DR raises the question of conjunctival epithelial cell an tigen presentation; The epithelial cytokines which are upregulated are know n to promote eosinophilic inflammation and are typical of allergic inflamma tion. The differences in cytokine patterns may be exploitable for future th erapy. (C) 1998 Academic Press.