LL-37 — 5mg

LL-37 is the sole cathelicidin antimicrobial peptide expressed in humans, cleaved proteolytically from its precursor hCAP-18 by neutrophil protease-3 at sites of infection or injury. The peptide's 37-amino acid amphipathic α-helical structure allows it to insert into and disrupt bacterial membranes through a carpet-like mechanism, producing rapid, broad-spectrum antimicrobial activity against Gram-positive bacteria, Gram-negative bacteria, fungi, and enveloped viruses. Unlike classical antibiotics, LL-37 kills through physical membrane disruption rather than targeted biochemical inhibition — making resistance development mechanistically difficult.

Antimicrobial activity, however, is only part of the peptide's biological role. LL-37 is a potent immunomodulator: it neutralizes circulating LPS to dampen septic shock responses, recruits neutrophils and monocytes to infection sites through FPRL1 signaling, promotes angiogenesis during wound healing, and modulates dendritic cell maturation to shape adaptive immune responses. This dual role — direct pathogen killing plus immune orchestration — positions it as a central node in host defense and a research focus for both infectious disease and wound healing applications.

Clinical and preclinical research has examined LL-37 in chronic non-healing wounds (diabetic ulcers, venous stasis ulcers), atopic dermatitis (where LL-37 expression is reduced), and antimicrobial resistance applications. Paradoxically, elevated LL-37 expression is implicated in psoriasis pathogenesis, where the peptide complexes with self-DNA to trigger plasmacytoid dendritic cell activation — an example of how host defense molecules can contribute to autoimmunity when dysregulated. The peptide's dual antimicrobial-immunomodulatory activity makes it a frequent target for synthetic analog development aimed at retaining antimicrobial function while tuning immune effects.