Effect of chronic antigen inhalation in guinea pigs

To examine the role of airway inflammation in airway hyperresponsiveness (AHR), we examined the effect of chronic antigen inhalation in sensitized guinea pigs. Guinea pigs were actively sensitized with dinitrophenylated Ascaris suum extract (DNP-As) and repeatedly exposed to aerosolized DNP-As antigen once a day for 4 or 10 days. Twenty-four hours after the last antigen exposure, airway responsiveness to inhaled acetylcholine (ACh) and bronchoalveolar lavage (BAL) were studied. The guinea pigs receiving 4 days of exposure to antigen demonstrated an increase in airway responsiveness to inhaled ACh (p < 0.05). On the other hand, the guinea pigs receiving 10 days of exposure to antigen showed no significant change in airway responsiveness to inhaled ACh. BAL fluid analysis indicated that a significant increase in the number of eosinophils and neutrophils was observed in both groups of guinea pigs. A significant increase in the number of lymphocytes in BAL fluid was observed in guinea pigs exposed for 10 days, but not in those exposed for 4 days. We conclude that repeated exposure to antigen induced both development and suppression of AHR. Our results suggest that airway inflammation may play a role in both the development and suppression of AHR.