Airway Eosinophils from Actively Sensitized Guinea Pigs Exhibit Enhanced Superoxide Anion Release in Response to Antigen Challenge

Antigen challenge of actively sensitized guinea pigs produces airway eosinophilia, airway hyperreactivity, and late-phase bronchoconstriction. The recruited eosinophils are thought to be important cells in the development of the airway hyperreactivity and the late-phase bronchoconstriction. However, the functional abilities of these eosinophils have not been determined in response to antigen challenge. The purpose of this study was to describe the characteristics of superoxide anion release from airway eosinophils obtained 24 h after ovalbumin challenge of actively sensitized guinea pigs. Eosinophils were collected by bronchoalveolar lavage. The total bronchoalveolar lavage eosinophil count was 17- to 27-fold greater in sensitized, ovalbumin-challenged guinea pigs (9.30 ± 0.11 × 106/guinea pig) than in unsensitized guinea pigs (0.35 ± 0.07 × 106/guinea pig) or sensitized, saline-challenged guinea pigs (0.56 × 106/guinea pig; n = 2). The increase in eosinophils was due to increased lavage leukocyte count and increased eosinophil differential. Eosinophils were isolated on a Percoll-plasma discontinuous gradient. Two populations of eosinophils were collected, one at the 1.093 g/ml gradient step and one at the 1.107 g/ml gradient step. Unstimulated or phorbol myristate acetate (PMA)-stimulated superoxide anion release was measured by the reduction of ferricytochrome c. Unstimulated superoxide anion release from both eosinophil populations of challenged guinea pigs (4.50 ± 2.37 and 4.07 ± 1.48 nmol from 1.093 and 1.107 g/ml eosinophils, respectively) was 6- to 7-fold greater than superoxide anion release from eosinophils of control guinea pigs (0.74 ± 0.43 and 0.56 ± 0.25 nmol from 1.093 and 1.107 g/ml eosinophils, respectively). Superoxide anion release, from eosinophils of challenged guinea pigs, was also enhanced 2- to 4-fold in response to low PMA doses (10−11 and 10−9 M) compared to superoxide anion release from eosinophils of control guinea pigs. However, superoxide anion release in response to maximal PMA doses (10−7 M) was unaltered. Both eosinophil populations from sensitized, ovalbumin-challenged guinea pigs had an increased sensitivity to PMA as illustrated by a decrease in the half-maximal PMA dose for superoxide anion release. These data suggest that ovalbumin challenge of actively sensitized guinea pigs produced airway eosinophilia and enhanced eosinophil function.