Fig. 1

Semiquantitative measurement of Krüppel-like factor 5 (KLF5) production in the small airways by immunohistochemical staining. Lung tissues were obtained from control subjects that never or previously smoked and from former smokers with COPD. The localization of KLF5 in the lung tissues was investigated by immunostaining. Representative photographs of the immunoreactivity of KLF5 in the small airways are shown (original magnification × 200 for upper panels and left middle panel, × 400 for right middle panel; scale bars = 100 μm) (a). A negative control sample was provided to replace a non-specific polyclonal rabbit IgG antibody instead of the primary antibody on the lung tissue specimens of the patients with COPD. Arrow heads indicate KLF5-immunopositive cells. The immunopositive area of KLF5 in the small airways was quantified using Image J (b). **p < 0.01 versus control never smoker, ^†† p < 0.01 versus control ex-smoker