In research literature, LL-37 is generally treated as a 37-residue human cathelicidin antimicrobial peptide (the C-terminal domain of hCAP18), studied in membrane-disruption and innate-immune signalling assay models. LL-37 is a 37-residue human cathelicidin antimicrobial peptide (the C-terminal domain of hCAP18) that adopts an amphipathic α-helix at physiological ionic strength. It disrupts bacterial membranes, signals through formyl-peptide receptor-like 1 (FPRL1/FPR2), and modulates innate immune pathway outputs in human cell models. Its activity and aggregation state are strongly ionic-strength dependent, which makes buffer conditions a critical experimental variable.
Research using LL-37 typically separates its direct membrane-disrupting activity from its receptor-mediated immunomodulatory signalling, using FPRL1/FPR2 antagonists to attribute readouts to the receptor pathway. Because high salt promotes immediate aggregation, careful buffer control is central to reproducible results. For laboratory teams, the practical emphasis is usually on sequence identity, receptor or pathway relevance where documented, and whether LL-37 behaves consistently across stability, purity, and analytical verification workflows. Variant labels on this page support clearer internal referencing when multiple labelled variants are under review.