Influence of local antigen exposure dose in the upper respiratory tract on sensitization with cedar pollen

Abstract

An increase in Japanese cedar pollen counts is the probable reason for the increase in the number of Japanese cedar hay fever patients. To determine whether local antigen exposure dose affects sensitization with cedar pollen, we compared serum levels of specific IgE antibody in rats exposed to higher and lower doses of cedar pollen antigen through the nose. Serum levels of cedar pollen-specific IgE antibody was examined in Brown Norway rats exposed to a higher dose of (20 μg) Cry j I, a lower dose (2 μg) of Cry j I or no dose for 6 months. Serum levels of cedar pollen-specific IgE antibody were measured by reverse IgE-capture ELISA. The extent of local eosinophilia in the nasal, laryngeal and tracheal mucosa of rats exposed higher and lower doses of cedar pollen antigen and controls were observed microscopically. The mean serum levels of specific IgE antibody in rats exposed to the higher dose were significantly higher than those in rats exposed to the lower dose, and the mean levels in rats in the lower-dose group were significantly higher than in controls. The extent of eosinophilia in the nasal mucosa in the higher-dose group was significantly greater than in controls, but no significant differences between the lower-dose group and controls were found. The extent of eosinophilia in the laryngeal mucosa in the higher-dose group was significantly greater than that in the lower-dose group and in controls. Only a small degree of eosinophilia was observed in the trachea of all three groups. Local exposure dose of the upper airway to cedar pollen may affect sensitization.