and induce clumping agglutination of bacteria, a major antibacterial function for salivary proteins. For example, BPIFA2 protein was shown to inhibit the growth of Pseudomonas aeruginosa, although it did not cause agglutination of these bacteria. Like BPIFA1/PLUNC which acts as a surfactant to lower the surface tension in mucosal fluids, BPIFA2/PIP also is a crucial surfactant in saliva. When the gene is silenced in a knockout mouse, the saliva exhibits the surface tension of water. 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. References External links Human proteins Genes Genes on human chromosome 20