Figure 1.

Control-derived airway epithelial cells co-cultured with NTHi exhibit frequent autophagic events, and that may clear invading bacteria before they can be clearly identified within the cytoplasm. Control human air–liquid interface cultures exhibiting mucociliary differentiation and three-dimensional growth characteristics were assessed. (A) An airway epithelial cell (AEC) exhibits active degradative processes after 24 h co-culture with NTHi, and which may represent the final stages of clearing intracellular NTHi. Extracellular NTHi is also observed above the apical aspect of the cell (white arrow). (B) Multiple double membrane structures (white arrows), indicative of autophagosomes containing a circular cargo of similar morphology and size (approx. 500 nm) as NTHi, but which lack the distinct morphology observed for NTHi identified within COPD-derived AEC. Also shown is a double membrane phagophore (double white arrows). (C) Another example of an AEC which exhibits degradative activity. Here autolysosomes are observed at the final stage of a degradative process (white box). (D) The autolysosomes are magnified in D (two are indicated with single white arrows). Further in D, a nearby autophagosome (double white arrow) is also resolved. Data is representative of n=3 control AEC donor cultures.