LL-37 Is an antimicrobial peptide which belongs to the cathelicidin family of AMPs(antimicrobial peptides). LL-37, like cathelicidins, are stored in neutrophil granules as inactive precursors and are released as mature peptides when neutrophils are stimulated. LL-37 is expressed in various cells and tissues such as circulating neutrophils and myeloid bone marrow cells, epithelial cells of the skin, and is also expressed in the gastrointestinal tract, as well as in the epididymis and lungs. Moreover, production of LL-37 in macrophages is stimulated by vitamin D released by sunlight through the skin. LL-37 plays an important role in the first line of defense against infection and systemic invasion of pathogens at sites of inflammation and wound. It is cytotoxic to both bacterial and normal eukaryotic cells and is significantly resistant to proteolytic degradation in solution. LL-37 shows a broad spectrum of antimicrobial activity against bacteria,
enveloped viruses, and fungi. It has also demonstrated success in helping promote wound healing but it may play a negative role in atopic dermatitis and psoriasis.