When viewed in combination, these results suggest (i) that free NE activity is inhibited as long as the antiprotease shield composed of NE inhibitors such as α1-antitrypsin and secretory leukocyte protease inhibitor (SLPI) is not overwhelmed [26, 42, 43] and (ii) that surface-bound NE activity may play a critical role in tissue damage, even in early CF lung disease with moderate airway neutrophilia [15]. This evidence concerns the gene ELANE and cystic fibrosis.