[5] This protein has been characterized in mammals such as rodents, carnivores, even-toed ungulates, insectivores, bats, lagomorphs, and shrews[6] but is apparently absent in primates and other vertebrates such as birds, reptiles, and amphibians.

[10] 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.Genes for the BPI/LBP/PLUNC superfamily are found in all vertebrate species, including distant homologs in non-vertebrate species such as insects, mollusks, and roundworms.

The PIFB9P pseduogene in humans was first reported in 2011 as a member of the BPI/LBP/PLUNC family,[13][12] but clones containing PIFB9P had been detected in 1999 genomic screening by the Welcome Trust Sanger Institute.

Although identified multiple times by independent scientists as a pseudogene not capable of coding for a protein, its gene sequence may predict two transcripts (splice variants) [15] and RNA transcripts detected by RNA-Seq screens have been observed in brain tissues, striated muscle, white blood cells (granulocytes, monocytes), and esophageal mucosa.

[20] Those odorant receptors, in turn, are associated with nasal epithelial cells integrated with olfactory neurons that project back to the brain's oflactory areas and hypothalamus.