LL-37, also known as CAP-18, is an antimicrobial peptide. Research has shown that it possesses antimicrobial, antiviral, and anti-fungal properties. LL-37 has also been shown to reduce inflammation, promote wound closure, killing bacteria, but have been found to have other dramatic effects as well. and encourage blood vessel growth in specific settings. LL-37, also called CAP-18 (catatonic antimicrobial protein 18), is an antimicrobial peptide expressed in almost all tissues and organs. It is produced by many cell types, including macrophages, airway epithelial cells, skin, and ocular epithelial cells, and natural killer (NK) cells.
Multiple studies have been conducted on LL-37 since its discovery in 1995. These studies show that LL-37 induces an anti-cancer effect in colon cancer and gastric cancer. This natural peptide can also modulate the development of inflammatory and autoimmune diseases. In a mice model of collagen-induced arthritis, LL-47 reportedly played a protective role. It has also been found to kill gram-negative bacteria through direct anti-bacterial activities as well as modulation. Plus, it has been shown to promote wound closure in lung disease. LL-37 has also been shown to down-regulate the signaling of specific toll-like receptors (TLRs), thereby decreasing the production of pro-inflammatory cytokines. It has also exhibited anti-inflammatory effects, mainly by blocking the signaling of gram-negative bacteria.