Background: Lack of evidence on the inflammatory cell populations in ACO airways has led to their poor prognosis and treatment.

Aim: To enumerate inflammatory cell changes in the airway wall of ACO and compare them with asthma (AS), COPD current smokers (CS) and ex-smokers (ES), normal lung function smokers (NLFS) and non-smoker controls (HC).

Methods: A total of 144 immunohistochemically stained endobronchial biopsy tissues from pathological groups and HC were evaluated for macrophages (MPs), neutrophils (NLs), eosinophils, mast cells (MCs), CD4+, and CD8+ T cells in the epithelium (EPI), reticular basement membrane (RBM), and lamina propria (LP) up to 120?µM deep using Image-Pro Plus 7 software.

Results: We found that the number of MPs in ACO tissue was much higher in the EPI and RBM than in HC (p<0.001 for both), COPD-ES (p<0.001 for both), and -CS (p<0.05 and <0.0001, respectively). The ACO LP MPs were substantially higher than COPD-CS (p<0.05). MCs in ACO were significantly lower than NLFS (p<0.05) in the EPI; lower than COPD (p<0.05) and NLFS (p<0.001) in RBM; and lower than HC (p<0.05) in LP. We noted reduced eosinophils in the ACO LP than HC (p<0.05) and the lowest NLs in ACO and asthma. Furthermore, CD8+ cells increased in the ACO RBM compared to HC (p<0.05), COPD-ES (p<0.05), and NLFS (p<0.01); however, they were similar in the epithelium and LP across groups. CD4+ cells remained lower across all regions and groups.

Conclusion: These results show that the inflammatory cellular profile of ACO airway tissue was different from that of asthma and COPD, with MPs being the predominant cell type.