The function of Ensembl gene identifier ENSG00000198183 (BPIFA1, BPI fold containing family A member 1) is as follows. Lipid-binding protein which shows high specificity for the surfactant phospholipid dipalmitoylphosphatidylcholine (DPPC) (PubMed:25223608). Plays a role in the innate immune responses of the upper airways (PubMed:23132494, PubMed:23499554). Reduces the surface tension in secretions from airway epithelia and inhibits the formation of biofilm by pathogenic Gram-negative bacteria, such as P.aeruginosa and K.pneumoniae (PubMed:23132494, PubMed:23499554, PubMed:27145151). Negatively regulates proteolytic cleavage of SCNN1G, an event that is required for activation of the epithelial sodium channel (ENaC), and thereby contributes to airway surface liquid homeostasis and proper clearance of mucus (PubMed:24043776, PubMed:24124190). Plays a role in the airway inflammatory response after exposure to irritants (PubMed:11425234). May attract macrophages and neutrophils (PubMed:23132494). {ECO:0000269|PubMed:11425234, ECO:0000269|PubMed:23132494, ECO:0000269|PubMed:23499554, ECO:0000269|PubMed:24043776, ECO:0000269|PubMed:24124190, ECO:0000269|PubMed:25223608, ECO:0000269|PubMed:27145151}.