[8] The BPI fold creates apolar binding pockets that can interact with hydrophobic and amphipathic molecules, such as the acyl carbon chains of lipopolysaccharide found on Gram-negative bacteria, but members of this family may have many other functions.

[14] It is primarily secreted into saliva and is therefore among the first line of defense against pathogens entering the mouth.

[15] For example, BPIFA2 protein was shown to inhibit the growth of Pseudomonas aeruginosa, although it did not cause agglutination of these bacteria.

When the gene is silenced in a knockout mouse, the saliva exhibits the surface tension of water.

[17] Further, without BPIFA2/PIP, levels of LPS in saliva were lower than in normal mice and the knockout mice exhibited signs of endotoxemia, suggesting bacteria were bypassing the first line of defense and passing into the digestive tract to cause mild inflammation.