Bpifb1, also known as Lplunc1, belongs to the BPI-fold-containing family and is a natural immune protection molecule. It contains 16 exons and 15 introns, encoding 484 amino acids with a 19-amino-acid signal peptide sequence at the 5' terminal. It can respond to external physical and chemical stimuli, and is involved in regulating chronic infections, inflammation, and may play important roles in tumor development and respiratory diseases [2].

In Bpifb1 knockout (KO) mice, effective mucociliary clearance (MCC) in vivo is diminished. The reduction in MCC occurs without defects in epithelial ion transport or ciliary beat frequency. Loss of Bpifb1 in vivo and in vitro alters the biophysical and biochemical properties of mucus related to impaired MCC, and BPIFB1 and MUC5B are colocalized in secretory granules in mice and the protein mesh of secreted mucus in human airway epithelia cultures, indicating Bpifb1 is an important component of the mucociliary apparatus and mucus protein network [1].

In conclusion, Bpifb1 is crucial for maintaining the normal function of the mucociliary apparatus and mucus properties. The Bpifb1 KO mouse model has revealed its significance in MCC, which is related to host defense in the airway. Additionally, its abnormal expression is associated with various diseases such as nasopharyngeal carcinoma, breast cancer, and cystic fibrosis, suggesting its potential roles in tumor development and respiratory disease regulation [1,2,3,4,5].