Calhoun, William J.

Abstract Airway inflammation is increasingly recognized as a pivotal component of asthma. Because allergens provoke bronchial constriction and inflammation in allergic subjects, bronchial antigen challenge has emerged as a powerful technique for evaluating mechanisms involved in this process. In this study, we compare whole lung antigen challenge (WLAC) with segmentai bronchoprovocation (SBP) in eight allergic, non-asthmatic, non-smoking subjects, and evaluated the response by bronchoalveolar lavage (BAL) prior to, and 48 h after antigen challenge. Both challenge techniques evoked airway inflammation, manifest as an increase in total cells and eosinophils recovered by BAL, an increase in total protein concentration, and enhanced production of superoxide anion by airspace cells. The degree to which these changes occurred was significantly greater with SBP than WLAC, and only SBP evoked persistent measurable change in alveolar macrophage density and eosinophil granule protein concentrations. Moreover, although both techniques were associated with a comparable immediate fall in FEV1, only WLAC resulted in statistically significant persistent physiologic changes 48 h afterwards. We conclude that, as anticipated, SBP produces more intense airway inflammation in allergic subjects, does not result in late airway obstruction, and offers specific advantages in studying allergen-driven airway inflammation.

Abstract The mechanism of airway eosinophilia during antigen-induced inflammation was investigated by measurement of eosinophil-active cytokines utilizing an eosinophil survival assay. In the first study, 4 patients with allergic rhinitis underwent segmental bronchoprovocation (SBP) with low, medium, and high doses of ragweed extract instilled into different bronchial subsegments; bronchoalveolar lavage (BAL) fluids were collected from each segment 12 min and 48 h after challenge. Eosinophil granule proteins and eosinophil survival activity were significantly elevated in the 48-h (late-phase) BAL fluids from these segments. Correlations were observed between the concentrations of eosinophil granule proteins and eosinophil survival activity (rs = 0.717 to 0.880, p < 0.001) in BAL fluids. Eosinophil survival activity was completely neutralized by anti-IL-5 monoclonal antibody in five of the seven 48-h samples tested representing three of the 4 patients. In the two remaining samples, eosinophil survival activity was only partially neutralized by either anti-IL-5 antibody or anti-granulocyte-macrophage colony-stimulating factor (GM-CSF) but was completely neutralized by anti-IL-5 and anti-GM-CSF in combination. Subsequently, in the second study, 10 patients with allergic rhinitis were challenged by SBP with ragweed extract. Eosinophil survival activity was significantly elevated in the 48-h BAL fluids; this activity was partially neutralized by anti-IL-5 antibody about (48%) and completely neutralized by the combination of anti-IL-5 and anti-GM-CSF antibodies. These findings suggest that the eosinophil survival activity in the late inflammatory lesions following SBP with allergen is mainly associated with IL-5, with small contributions from GM-CSF. Thus, IL-5 is the predominant eosinophil-active cytokine present in BAL fluids during allergen-induced late-phase inflammation and may play a key role in the pathophysiology of allergen-induced, eosinophil-predominant airway inflammation.

Abstract The effect of zafirlukast (Z) to alter the inflammatory response to segmental antigen challenge (SAC) was assessed by bronchoalveolar lavage (BAL) in this double-blind, placebo-controlled, two-period, crossover trial in 11 allergic asthmatic patients. Patients with asthma and positive skin tests to antigen received 7 d of treatment with Z (20 mg twice daily) or placebo (P) during two trial periods 14 to 21 d apart. At steady state (Day 5), patients underwent SAC followed by BAL immediately after challenge and 48 h later. Purified alveolar macrophages were analyzed ex vivo for phorbol myristate acetate (PMA)-driven superoxide release. Results were analyzed by analysis of variance (ANOVA). Forty-eight hours after SAC, Z therapy was associated with significantly reduced BAL lymphocytes and alcian blue–positive cells (presumably basophils) compared with P (p < 0.01), with a trend toward reduced numbers of alveolar macrophages (p = 0.06). PMA-driven superoxide release by purified alveolar macrophages was significantly reduced 48 h after SAC in the Z versus P arms (p < 0.05). Reduction of basophil influx, mediator release, and cellular activation may be important in attenuating the late phase of asthma. Collectively, the data suggest that zafirlukast therapy alters cellular infiltration and activation associated with antigen challenge.