Differential distribution of inflammatory cells in large and small airways in smokers

¹ Università di Palermo, Italy
² Sao Paulo University, Brazil
³ Leiden University Medical Centre (LUMC), Netherlands
⁴ Leiden University Medical Centre (LUMC), Italy

^* To whom correspondence should be addressed. E-mail: p.s.hiemstra{at}lumc.nl.

Accepted 20 July 2006

	Abstract

RATIONALE: Smoking induces structural changes in the airways and is considered as a major factor in the development of airflow obstruction in chronic obstructive pulmonary disease (COPD). However differences in inflammatory cell distribution between large and small airways have not been systematically explored in smokers. We hypothesized that the content of cells infiltrating the airway wall differs between large and small airways.

AIMS: We compared the content of neutrophils, macrophages, lymphocytes and mast cells infiltrating large and small airways in smokers who underwent surgery for lung cancer.

METHODS: Lung tissue from fifteen smokers was analysed. Inflammatory cells in the lamina propria were identified by immunohistochemistry and quantified by digital image analysis and expressed in number of cells per surface area.

RESULTS: The number of neutrophils infiltrating the lamina propria of small airways (median: 225.3 cells/mm²) was higher than that in the lamina propria of large airways (median: 60.2 cells/mm²; p =0.0001). Similar results were observed for mast cells: 313.3 cells/mm² and 133.7 cells/mm² in the small and large airways, respectively (p =0.0002). In contrast, the number of CD4⁺ cells was higher in large airways compared to small airways (median: 217.8 versus 80.5 cells/mm²; p =0.042).

CONCLUSIONS: These findings indicate a non-uniform distribution of neutrophils and mast cells throughout the bronchial tree and suggest that these cells may be involved in the development of smoking-related peripheral lung injury.

Key Words: COPD, Neutrophils, lymphocytes, mast cells, smoking