Bronchoalveolar lavage and histologic characterization of late asthmatic response in guinea pigs.

To elucidate the mechanisms of late asthmatic response (LAR) observed in asthmatic subjects, we have developed an animal model of LAR using guinea pigs. Fifty guinea pigs were immunized with a mixture of Ascaris suum extract and aluminum hydroxide and then challenged with an inhalation of Ascaris suum extract without anesthesia. Twenty of the 50 guinea pigs showed a dual asthmatic response in which the LAR occurred 3 to 6 h after immediate asthmatic response (IAR). Histologic studies by rapid freezing with liquid nitrogen or bronchoalveolar lavage (BAL) were performed in 14 of these 20 guinea pigs with LAR and compared with those in 10 of 18 guinea pigs with only IAR, 10 control guinea pigs, and 10 nonimmunized but challenged guinea pigs. Both the percentage and the absolute number of neutrophils in the BAL fluid of the guinea pigs with LAR were significantly greater than those of the control guinea pigs (p less than 0.02) and than those of the nonimmunized but challenged guinea pigs (p less than 0.02). However, that of guinea pigs with LAR was not significantly different from that of guinea pigs with only IAR. On the other hand, histologic examination showed that eosinophil infiltration within the airway walls of the guinea pigs with LAR was more prominent than that of the guinea pigs with only IAR, and showed that there was no significant difference in neutrophil infiltration within the airway walls between the guinea pigs with LAR and the animals with only IAR. Contraction of airway (bronchus, bronchiole) smooth muscle, submucosal edema, and mucus in airway lumen were also observed in LAR.(ABSTRACT TRUNCATED AT 250 WORDS)