CD4 and chronic obstructive pulmonary disease: Therefore, in this cross-sectional exploratory study, we performed an in-depth analysis of inflammatory cells, including macrophages, neutrophils, eosinophils, mast cells, CD8+ , and CD4+ T lymphocytes in the large airway EBB tissues of ACO, especially in the epithelium, RBM, and LP area, and compared them with asthma, COPD-ES and COPD-CS, HC, and NLFS.