SCGB1A1 and bronchiectasis: Here, we sought to investigate the spatial distribution and quantify airway progenitor cells with histologic assessment of specific markers, including TTF-1+ cells for multiple airway progenitors, P63+ for BCs, Club Cell 10 kDa Protein (CC10)+ for club cells and surfactant protein C (SPC)+ for AECII in the bronchiolar or alveolar epithelium of distal airways in bronchiectasis (Rawlins et al., 2009; Mou et al., 2012; Crystal, 2014; Jacob et al., 2017).