MMP-9 is associated with neutrophilic inflammation in COPD.

<p>(A) MMP-9 expression was positively associated with BALF neutrophils in GOLD IV COPD (Spearman r = 0.0.89, <i>p<0.001</i>). (B) MMP-9 activity was also positively associated with BALF neutrophils in GOLD IV COPD (Spearman r = 0.0.92, <i>p<0.001</i>), whereas no association was observed with BALF macrophages (C & D).