Biomedical Engineering Reference
In-Depth Information
ving the glands, gland ducts, and epithelial lining of the central airways (Fig.
4) and it is reasonable to postulate that the associated gland hypertrophy is
related to growth factors released during this chronic inflammatory process.
The introduction of fiberoptic bronchoscopy provided the opportunity
to biopsy the central airways more easily (19-26). These studies have shown
that the epithelium of the central airways contains eosinophils as well as
areas of both squamous and goblet cell metaplasia in COPD, and that the
thickness of the reticular basement membrane remains within the normal
range but may overlap the lower range of the values observed in asthma
(20,21). The epithelium and subepithelial tissue contain increased numbers
of neutrophils (20,21) and smaller numbers of eosinophils that tend to
increase during exacerbations of COPD (21), as well as an increase in the
numbers of mononuclear cells including mast cells (22) and lymphocytes
(23-26). Saetta et al. (23) and Kemeny et al. (24) have shown that the mono-
nuclear cells consist of a mixture T-lymphocytes that express markers of
early and late activation (24) and Di Stefano et al. (25) and O'Shaughnessy
et al. (26) found that there were greater numbers of CD8 than CD4 cells and
Figure 4
(A) Shows a low power photo micrograph of the bronchial wall that
demonstrates a normal mucus producing epithelial gland with its duct connecting
to the epithelial surface of the bronchial lumen. B and C show enlarged glands from
a patient with chronic bronchitis. The arrow and arrowhead in C point to inflamma-
tory cells in the gland tissue. (Photomicrograph in A was taken by the late professor
William M Thurlbeck. From Ref. 12.)
