LL-37

LL-37 is the only cathelicidin-derived antimicrobial peptide in humans, processed from the C-terminus of the precursor protein hCAP18 (human cationic antimicrobial protein 18). This 37-amino acid peptide beginning with two leucines represents a critical component of innate immunity found in neutrophils, epithelial cells, and various body fluids. LL-37 exhibits broad-spectrum antimicrobial activity against bacteria, fungi, and viruses through membrane disruption and immunomodulatory mechanisms. Beyond direct antimicrobial effects, research demonstrates LL-37 promotes wound healing, stimulates angiogenesis, modulates inflammatory responses, and influences adaptive immunity. The peptide can neutralize bacterial lipopolysaccharide (LPS), reducing inflammatory signaling. Studies indicate potential applications in wound healing, infection control, and inflammatory conditions. LL-37 expression is induced by vitamin D, linking vitamin D status to immune function. Dysregulation of LL-37 has been implicated in various conditions including rosacea, psoriasis, and atherosclerosis, highlighting its complex role in health and disease.

Clinical evidence is limited to topical use in chronic wounds; trials are modest in size and mostly single-country, with no data supporting systemic administration. Formulation and dosing for research use are not standardized, and long-term safety data are lacking.

Endogenous human cathelicidin (37 amino acids) cleaved from hCAP18; acts via membrane disruption and immunomodulatory signaling. Exogenous delivery in trials has been topical (cream); a short biological half-life limits systemic use.