LL-37, the neutrophil granule- and epithelial cell-derived cathelicidin, utilizes formyl peptide receptor-like 1 (FPRL1) as a receptor to chemoattract human peripheral blood neutrophils, monocytes, and T cells

We have previously shown that antimicrobial peptides like defensins have th e capacity to mobilize leukocytes in host defense. LL-37 is the cleaved ant imicrobial 37-residue, COOH-terminal peptide of hCAP18 (human cationic anti microbial protein with a molecular size of 18 kD), the only identified memb er in humans of a family of proteins called cathelicidins. LL-37/hCAP18 is produced by neutrophils and various epithelial cells. Here we report that L L-37 is chemotactic for, and can induce Ca2+ mobilization in, human monocyt es and formyl peptide receptor-like 1 (FPRL1)-transfected human embryonic k idney 293 cells. LL-37-induced Ca2+ mobilization in monocytes can also be c ross-desensitized by an FPRL1-specific agonist. Furthermore, LL-37 is also chemotactic for human neutrophils and T lymphocytes that are known to expre ss FPRL1. Our results suggest that, in addition to its microbicidal activit y, LL-37 may contribute to innate and adaptive immunity by recruiting neutr ophils, monocytes, and T cells to sites of microbial invasion by interactin g with FPRL1.