Exposure to diesel exhaust aggravates nasal allergic reaction in guinea pigs

Diesel exhaust particulates (DEP) () and exposure to diesel exhaust (DE) induce nasal mucosal hyperresponsiveness to histamine. Therefore, in the present study, we investigated whether or not exposing guinea pigs to DE aggravates the nasal allergic reaction induced by repeated nasal administration of ovalbumin (OVA). Guinea pigs were exposed to filtered air or to DE (DE containing 0.3 or 1.0 mg/m(3) of DEP) for 5 wk. During exposure to filtered air or to DE, guinea pigs were administered 1% of OVA in saline into the nasal cavities once a week. Sneezes were counted and nasal secretions were measured as indices of sneezing responses and rhinorrhea for 20 min after OVA administration. Titers of specific anti-OVA-IgG and anti-OVA-IgE and the number of eosinophils infiltrated into both nasal epithelium and subepithelium were measured at the end of the exposure to DE. Exposure to DE enhanced the number of sneezes and the amount of nasal secretions induced by OVA. Titers of specific anti-OVA-IgG and anti-OVA-IgE also significantly increased in DE-exposed animals. Exposure to DE also augmented the number of eosinophils that infiltrated both the nasal epithelium and the subepithelium induced by OVA. These results suggest that exposure to DE enhances the nasal allergic reaction induced by repeated antigen administration in guinea pigs.