Expression of ICAM-1 on conjunctival epithelium and ECP in tears and serumfrom children with allergic conjunctivitis

Background: Conjunctival eosinophilia may be considered to be an indicator of conjunctival allergic disease. The absence of eosinophils on conjunctiva l scraping, however, cannot rule out the diagnosis of allergic conjunctivit is because eosinophil infiltration may be deeper in conjunctival tissue. Eo sinophil cationic protein (ECP) is a toxic product secreted by activated eo sinophil as a marker of eosinophil activation. Eosinophil cationic protein concentrations in body fluids correlate with the severity of some allergic diseases. ICAM-1 promotes adhesion of leukocytes to epithelium, endothelium , and upregulates inflammation. Expression of adhesion can be modified by m any extracellular and intracellular variables such as proinflammatory cytok ines, extracellular matrix proteins, and viral infection. Objective: We investigated whether local eosinophils are only activated in conjunctival epithelium or circulating activated eosinophils are involved i n peripheral blood during allergic reaction of the eye. We also demonstrate d the possible expression of ICAM-1 on epithelial cells from conjunctival s craping and compared them with soluble ICAM-1 values of serum and tears in children with allergic conjunctivitis and healthy children. Methods: Seventeen subjects were selected on the basis of clinical manifest ations, history, skin prick test, and total serum IgE. A microcapillary tub e was used to collect the tears from the inner canthus. Conjunctival epithe lia were obtained by scraping the upper tarsal conjunctiva. The level of EC P was measured by the CAP system, soluble ICAM-1 was measured by ELISA, and ICAM-1 on conjunctival epithelial cells were expressed by the avidine-biot in peroxide complex procedure. Results: Serum IgE and the eosinophil count were increased in 10 out of 17 patients, positive skin prick tests were positive in 11 patients (Dematopha goides pternyssinus; 9, Demzatophagoides farinae: 8), and eosinophilia in c onjunctival epithelium was in 11 patients (4 patients: >3/HPF, 7 patients: 1-3/HPF). The ECP levels in tears were significantly increased in the patie nt group (12.0 +/- 8.0 versus 3.9 +/- 3.8 mu g/mL, P = .01), but not in ser um (52.5 +/- 43.1 versus 28.3 +/- 25.9 mu g/mL). There is significant corre lation between the eosinophil count in peripheral blood and on conjunctival epithelium (P = .007, r = .62; n = 25). The ICAM-1 expression score on con junctival epithelial cells was significantly different between the patient group and controls (patient group: 1.77 +/- 2.25 versus control: 0.13 +/- 0 .35 ng/mL, P = .002). There was a significant correlation between ICAM-1 ex pression on conjunctival epithelial cells and the ECP levels of tears (P = .01, r = .58; n = 25). Soluble ICAM-1 levels in serum and tears showed no s ignificant difference between the patient group and controls, and also, the re was no correlation between sICAM-1 levels in the serum and tears. Conclusion: Eosinophil cationic protein in tears and ICAM-1 expression scor es on conjunctival epithelium showed a significant difference between child ren with allergic conjunctivitis and the healthy controls, but circulating ECP and sICAM-1 in serum were not significantly different between the two g roups. These results may suggest that ICAM-1 is locally upregulated in infl ammation, mediating eosinophil activation and migration to conjunctival epi thelium, but is not involved as inflammatory mediators in peripheral blood during allergic response in children with allergic conjunctivitis.