In this study the lung tissue obtained from surgical resection in 159 patients was examined to correlate pathological findings in the small airways with the severity of COPD using the GOLD classification. The percentage of airways containing polymorphonuclear neutrophils, macrophages, CD4 cells, CD8 cells, B cells, and lymphoid follicles increased with disease progression. The volume of B cells and CD8 cells also increased with increasing severity of COPD. The progression of COPD through GOLD stages 0–4 was most strongly associated with thickening of the airway wall and each of its components. This is a reflection of the repair or remodelling process within the lung. Disease progression was also associated with the degree of inflammatory response and occurrence of lymphoid follicles in the airway wall, and the presence of mucous exudates within the airway lumen.

This study shows that the adaptive immune response may play a key role in the persistent inflammation associated with COPD. This, and other factors such as infection, are likely to lead to changes in the airway wall that contribute to the small airways obstruction in COPD.