Background: Eosinophils but not neutrophils may play a role in the airway inflammation of asthma. In chronic bronchitis (CB) and chronic obstructive pulmonary disease (COPD), neutrophils are present in the airways. To differentiate among the pathology of asthma, CB, and COPD eosinophils and neutrophils were studied in peripheral blood, bronchial biopsy specimens, and bronchoalveolar lavage fluid (BALF).
Methods: We studied nine nonsmoking healthy subjects, 20 nonsmoking patients with asthma, 10 nonatopic smoking patients with CB (forced expiratory volume in 1 second: 98.4% +/- 11.3%) and 17 patients with COPD (forced expiratory volume in 1 second: 51.2% +/- 14.3%). Eosinophils were characterized by their enumeration in biopsy specimens (EG2 monoclonal antibody), peripheral blood, and BALF and by measurement of eosinophil cationic protein in BALF. Neutrophils were characterized by their enumeration in biopsy specimens (anti-elastase monoclonal antibody) and BALF and by measurement of neutrophil-specific myeloperoxidase in BALF.
Results: In patients with asthma we found degranulated eosinophils in biopsy specimens and significantly increased eosinophil cationic protein levels in BALF. In patients with CB or COPD, eosinophil numbers in biopsy specimens were not significantly different from those of patients with asthma, but cells were not degranulated and eosinophil cationic protein levels in BALF were similar to those of normal subjects. In patients with CB or COPD neutrophils were not increased in the mucosa, but neutrophil numbers and myeloperoxidase levels in BALF were significantly increased.
Conclusion: The percentages of neutrophils in BALF were greater in patients with COPD than in those with CB, suggesting a role in the chronic airflow limitation.