NFKB1 and chronic obstructive pulmonary disease: Notably, the STRINGDB network not only emphasized the biological processes (such as cellular response to external stimulus, response to unfolded protein, mitochondrion organization, and apoptotic processes) most associated with COPD in AT2s but also contained the predicted signaling pathways (including NF-κB, IL-1, TNF, and MAPK signaling pathways) in AT2s influenced by ligands from monocytes (Fig. 4E).