Bronchial glands hypertrophy and goblet cell metaplasia occurs [1, 2]. This results in excessive mucous production or chronic bronchitis. Cell infiltrates also occur in bronchial glands.

Airway wall changes include squamous metaplasia of the airway epithelium, loss of cilia and ciliary dysfunction, and increased smooth muscle and connective tissue [2, 3].

Different inflammatory cells predominate in different compartments of the central airways. In the airways wall these are lymphocytes, predominantly of the CD8+ type, but as the disease progresses neutrophils also become prominent [4, 5]. In the airspaces, in addition to lymphocytes, neutrophils and macrophages can also be identified [6, 7].

Fig. 1. - a) A central bronchus from the lungs of a cigarette smoker with normal lung function; very small amounts of muscle are present; there are small epithelial glands. b) Bronchus from a patient with chronic bronchitis; shows a thick bundle of muscle and enlargement of glands. c) A higher magnification of the enlarged glands with evidence of chronic inflammation involving polymorphonuclear (arrow head) and mononuclear cells, including plasma cells (arrow). Printed with kind permission from J.C. Hogg and S. Green.