T helper type 17-related cytokine expression is increased in the bronchial mucosa of stable chronic obstructive pulmonary disease patients

Abstract

There are increased numbers of activated T lymphocytes in the bronchial mucosa of stable chronic obstructive pulmonary disease (COPD) patients. T helper type 17 (Th17) cells release interleukin (IL)-17 as their effector cytokine under the control of IL-22 and IL-23. Furthermore, Th17 numbers are increased in some chronic inflammatory conditions. To investigate the expression of interleukin (IL)-17A, IL-17F, IL-21, IL-22 and IL-23 and of retinoic orphan receptor RORC2, a marker of Th17 cells, in bronchial biopsies from patients with stable COPD of different severity compared with age-matched control subjects. The expression of IL-17A, IL-17F, IL-21, IL-22, IL-23 and RORC2 was measured in the bronchial mucosa using immunohistochemistry and/or quantitative polymerase chain reaction. The number of IL-22(+) and IL-23(+) immunoreactive cells is increased in the bronchial epithelium of stable COPD compared with control groups. In addition, the number of IL-17A(+) and IL-22(+) immunoreactive cells is increased in the bronchial submucosa of stable COPD compared with control non-smokers. In all smokers, with and without disease, and in patients with COPD alone, the number of IL-22(+) cells correlated significantly with the number of both CD4(+) and CD8(+) cells in the bronchial mucosa. RORC2 mRNA expression in the bronchial mucosa was not significantly different between smokers with normal lung function and COPD. Further, we report that endothelial cells express high levels of IL-17A and IL-22. Increased expression of the Th17-related cytokines IL-17A, IL-22 and IL-23 in COPD patients may reflect their involvement, and that of specific IL-17-producing cells, in driving the chronic inflammation seen in COPD.

Fig. 1

Photomicrographs showing the bronchial mucosa from (a) control non-smoker, (b) control healthy smoker with normal lung function, (c) mild/moderate stable chronic obstructive pulmonary disease (COPD) and (d) severe stable COPD immunostained for identification of interleukin (IL)-17A⁺ cells (arrows) in the bronchial submucosa. Results are representative of those from eight non-smokers, 11 healthy smokers, 14 mild/moderate COPD and 14 with severe COPD. E, epithelium; bar, 20 micron.

Fig. 4

Photomicrographs showing the bronchial mucosa from a patient with severe chronic obstructive pulmonary disease (COPD) double immunostained for identification of endothelial (CD31⁺) cells (coloured red) co-expressing interleukin (IL)-17A (a) (coloured brown) or IL-22 (b) (coloured brown) in the bronchial submucosa. IL-17A and IL-22 were revealed by diaminobenzidine substrate, whereas endothelial (CD31⁺) cells were revealed using fast red substrate. Arrows indicate double-stained bronchial vessels. E, epithelium; bar, 20 micron.

Fig. 3

Photomicrographs showing the bronchial mucosa from (a) control non-smoker, (b) control healthy smoker with normal lung function, (c) mild/moderate stable chronic obstructive pulmonary disease (COPD) and (d) severe stable COPD immunostained for identification of interleukin (IL)-23⁺ cells (arrows) in the bronchial epithelium. Results are representative of those from eight non-smokers, 11 healthy smokers, 14 mild/moderate COPD and 14 with severe COPD. E, epithelium; bar, 20 micron.

Fig. 2

Photomicrographs showing the bronchial mucosa from (a) control non-smoker, (b) control healthy smoker with normal lung function, (c) mild/moderate stable chronic obstructive pulmonary disease (COPD) and (d) severe stable COPD immunostained for identification of interleukin (IL)-22⁺ cells (arrows) in the bronchial submucosa. Results are representative of those from eight non-smokers, 11 healthy smokers, 14 mild/moderate COPD and 14 with severe COPD. E, epithelium; bar, 20 micron.

Fig. 5

Regression analysis between numbers of interleukin (IL)-22⁺ and CD4⁺ (a), IL-22⁺ and CD8⁺ (b) and IL-23⁺ and IL-17A⁺ (c) cells in the submucosa of all patients with chronic obstructive pulmonary disease (COPD). Correlation coefficients were calculated by using the Spearman's rank method.