The study shows that the human antimicrobial peptide LL-37 can help neutrophils (a type of white blood cell) release NETs, which are web-like structures that trap microbes. This effect happens at a concentration of about 5 micromolar and seems to rely on the peptide's oily (hydrophobic) parts. The researchers saw LL-37 move toward the cell nucleus and cause the nuclear membrane to break down, which is a key step in NET formation.

NETs (neutrophil extracellular traps) have been described as a fundamental innate immune defence mechanism. During formation of NETs, the nuclear membrane is disrupted by an as-yet unknown mechanism. In the present study we investigated the role of human cathelicidin LL-37 in nuclear membrane disruption and formation of NETs. Immunofluorescence microscopy revealed that 5 μM LL-37 significantly facilitated NET formation by primary human blood-derived neutrophils alone, in the presence of the classical chemical NET inducer PMA or in the presence of Staphylococcus aureus. Parallel assays with a random LL-37 fragment library indicated that the NET induction is mediated by the hydrophobic character of the peptide. The trans-localization of LL-37 towards the nucleus and the disruption of the nuclear membrane were visualized using confocal fluorescence microscopy. In conclusion, the present study demonstrates a novel role for LL-37 in the formation of NETs.