Neutrophilic respiratory tract inflammation and peripheral blood neutrophilia after grain sorghum dust extract challenge

Study objective: To determine if inhalation of grain sorghum dust in the laboratory would cause neutrophilic upper and lower respiratory tract inflammation in human volunteers, as well as systemic signs of illness. Design: Prospective. Setting: University of Nebraska Medical Center. Participants: Thirty normal volunteers. Interventions: Inhalation challenge with 20 mL of a nebulized solution of filter-sterilized grain sorghum dust extract (GSDE). One group received prednisone, 20 mg for 2 days, prior to the challenge. Measurements and results: Bronchoscopy with bronchoalveolar lavage (BAL) was performed 24 h after challenge, with samples collected as bronchial and alveolar fractions. Findings included visible signs of airways inflammation, quantified as the bronchitis index. The percentage of bronchial neutrophils was significantly increased in those challenged with GSDE vs the control solution, Hanks' balanced salt solution (40.3±4.5% vs 14.3±5.1%, p≤.01). Similar findings were seen in the alveolar fraction. Pretreatment with corticosteroids did not prevent the rise in neutrophils recovered by BAL. Peripheral blood neutrophils were also increased in volunteers challenged with the grain dust extract. To explain the increase in peripheral blood neutrophil counts, the capacity of the peripheral blood neutrophils to migrate in chemotaxis experiments was examined. The results demonstrate an increase in peripheral blood neutrophils and an increase in chemotactic responsiveness. Conclusions: Inhalation challenge with a grain dust extract causes respiratory tract inflammation and a peripheral blood neutrophilia. One reason for this may be an increase in activated peripheral blood neutrophils.