Background: The Th2 cytokine interleukin-13 (IL-13) has been implicated in the pathogenesis of chronic obstructive pulmonary disease (COPD). We sought to examine IL-13 expression in COPD subjects in induced sputum and bronchus specimens. We hypothesized that inflammatory cells expressing IL-13 localize to the airway smooth muscle bundle and bronchial glands.
Methods: Interleukin-13 was measured in sputum samples from subjects with COPD (n = 34) across a range of severity (Global initiative for chronic Obstructive Lung Disease 2-4) and controls (n = 14) using ELISA. IL-13+ cells and inflammatory cells were enumerated within surgically resected proximal airway using immunohistochemical techniques from subjects with COPD (n = 10), smoking (n = 10) and nonsmoking controls (n = 8).
Results: Sputum IL-13 was measurable in only 6/34 subjects with COPD and was not found in the smoking or nonsmoking control subjects. In subjects with COPD and controls there was a paucity of IL-13+ cells. The distribution of inflammatory cells within different airway compartments was similar in COPD and controls except for an increase in CD3(+) lymphocytes within bronchial glands in COPD (P = 0.04).
Conclusions: Our findings do not support a role for IL-13 in COPD. However, the tissue localization of inflammatory cells to airway compartments, particularly the increase of T cells in glands in COPD may be important in disease.