LL-37 is the only known human cathelicidin, which is a large protein family with diverse function. These peptides, which are primarily found in macrophages and polymorphonuclear leukocytes (both types of white blood cell), are important for killing bacteria, but have been found to have other dramatic effects as well. The entire class is often referred to as antimicrobial peptides (AMPs). LL-37 has been found to play important roles in autoimmune disease, cancer, and wound healing.
 
LL-37 is part of the innate immune system and as such is one of the first pieces of the immune system to be activated during infection. Research in skin infections suggests that normal skin has very low levels of LL-37 but that the peptide accumulates rapidly in the presence of invading pathogens. The peptide has been shown to work in tandem with other proteins, like human beta-defensin 2 to combat infection. 

LL-37 primarily works by binding to bacterial lipopolysaccharide (LPS), a major component of the outer membrane of gram-negative bacteria. LPS is a critical component of membrane integrity in these bacteria. The ability of LL-37 to bind to and interfere with LPS means it is exceptionally deadly to certain bacteria. There is interest in using the peptide exogenously to treat serious bacterial infections in people. 

Despite the fact that LL-37 acts on the cell membrane components of gram-negative bacteria, it still has potent gram-positive effects as well. This could make it a beneficial treatment for staph infections and other serious bacteria. In vitro research indicates that LL-37 enhances the effects of lysozyme, an enzyme responsible for the destruction of gram positive bacteria like Staph aureus. 
 
 
Peptides Canada