Effects of SO 2 exposure on allergic sensitization in the guinea pig

Abstract

The effect of sulfur dioxide (SO 2) exposure on local bronchial sensitization to inhaled antigen was studied in the guinea pig. Exposure to SO 2 (0.1 to 16.6 ppm) was performed in a 20 L exposure chamber for 8 hours on 5 consecutive days, while temperature, moisture, and concentration of SO 2 were monitored and kept constant. SO 2 concentrations were measured hourly by Schiff's reaction. On the last 3 days, SO 2 exposure was followed by inhalation of nebulized ovalbumin (OA) for 45 minutes. One week later, specific bronchial provocation with inhaled OA (0.1%) followed by plethysmographic measurements of airway obstruction were performed every 2 days during a 2-week period. Specific antibodies against OA were measured in serum and bronchoalveolar fluid by a direct enzyme immunoassay. The SO 2-exposed group (N = 17) demonstrated 67% to 100% positive bronchial reactions to inhaled OA, depending on the concentration of SO 2, whereas the control group without previous SO 2 exposure (N = 14) demonstrated bronchial reactions in only one animal (7%: p < 0.05). The degree of bronchial obstruction was significantly higher in the exposed group, compared to the control group, for all SO 2 concentrations ( p < 0.05). OA-specific antibodies in serum and bronchoalveolar fluid increased in SO 2-exposed groups significantly, compared to the control group ( p < 0.05). It is concluded from these results that exposure to SO 2 in low and medium concentrations can facilitate local allergic sensitization in the guinea pig.