Background and objective: The objective of this study was to enumerate total cells and the number of inflammatory cell differentials in large airways (LAs) versus small airways (SAs) of mild-moderate COPD, and against appropriate controls.

Methods: For LA, we used endobronchial biopsies and for SA resected lung tissues. Immunostaining was enumerated (cells per mm2 ) for macrophages, neutrophils, CD4 and CD8 T cells in the lamina propria (LP) up to 150 μM deep for LA and full wall thickness for SA.

Results: We confirmed hypocellularity in the LA and in the SA wall in smokers and COPD (P < 0.001). LA cellularity was least in current smokers with COPD (COPDCS) (P < 0.01), while SA cellularity was similar across smoker/COPD groups. LA neutrophils were decreased in COPD-CS (P < 0.01), while SA neutrophil counts were unchanged. Compared with controls, LA macrophage numbers in COPD were significantly lower (P < 0.05), with SA macrophage numbers unchanged. A significant increase was observed in SA CD8+ cells in both normal smokers (P < 0.01) and COPD-CS (P < 0.001) but not in LA.

Conclusion: These unique data indicate that the current model for airway wall inflammation in COPD is oversimplified, and contrast with innate inflammatory activation in the lumen, at least in mild-moderate disease. Any abnormalities in airway wall cell differentials are small, although exaggerated in percentage terms.