title: Antimicrobial peptide LL-37 promotes bacterial phagocytosis by human macrophages.
abstract: LL-37/hCAP-18 is the only human member of the cathelicidin family and plays an important role in killing various pathogens, as well as in immune modulation. In this study, we investigated the effect of LL-37 on bacterial phagocytosis by macrophages and demonstrate that LL-37 enhances phagocytosis of IgG-opsonized Gram-negative and Gram-positive bacteria in a dose- and time-dependent manner by dTHP-1 cells. In addition, LL-37 enhanced phagocytosis of nonopsonized Escherichia coli by human macrophages. Consistently, LL-37 elevated the expression of FcγRs on macrophages but not the complement receptors CD11b and -c. Further studies revealed that the expression of TLR4 and CD14 is also increased on LL-37-treated macrophages. Several lines of evidence indicated that the FPR2/ALX receptor mediated LL-37-induced phagocytosis. However, TLR4 signaling was also coupled to the phagocytic response, as a specific TLR4 antibody significantly suppressed phagocytosis of IgG-opsonized E. coli and nonopsonized E. coli by dTHP-1 cells. Finally, macrophages from Cnlp(-/-) mice exhibited diminished bacterial phagocytosis compared with macrophages from their WT littermates. In conclusion, we demonstrate a novel, immune-modulatory mechanism of LL-37, which may contribute to bacterial clearance.
authors.affiliation: Departments of Medical Biochemistry and Biophysics, Division of Physiological Chemistry 2, and.
authors.forename: Min
authors.initials: M
authors.lastname: Wan
authors.affiliation: Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Anne M
authors.initials: AM
authors.lastname: van der Does
authors.affiliation: Departments of Medical Biochemistry and Biophysics, Division of Physiological Chemistry 2, and.
authors.forename: Xiao
authors.initials: X
authors.lastname: Tang
authors.affiliation: Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Lennart
authors.initials: L
authors.lastname: Lindbom
authors.affiliation: Departments of Medical Biochemistry and Biophysics, Division of Physiological Chemistry 2, and Birgitta.Agerberth@ki.se jesper.haeggstrom@ki.se.
authors.forename: Birgitta
authors.initials: B
authors.lastname: Agerberth
authors.affiliation: Departments of Medical Biochemistry and Biophysics, Division of Physiological Chemistry 2, and Birgitta.Agerberth@ki.se jesper.haeggstrom@ki.se.
authors.forename: Jesper Z
authors.initials: JZ
authors.lastname: Haeggström
mesh_terms: D000818:Animals; D023181:Antimicrobial Cationic Peptides / Q000494:pharmacology* / Q000502:physiology; D002478:Cells, Cultured; D004926:Escherichia coli / Q000276:immunology; D006801:Humans; D007074:Immunoglobulin G / Q000276:immunology; D018950:Lipopolysaccharide Receptors / Q000032:analysis; D008264:Macrophages / Q000187:drug effects / Q000276:immunology*; D051379:Mice; D008810:Mice, Inbred C57BL; D010587:Phagocytosis / Q000187:drug effects*; D044042:Receptors, Formyl Peptide / Q000502:physiology; D017452:Receptors, IgG / Q000032:analysis; D051197:Toll-Like Receptor 4 / Q000032:analysis; D054804:Cathelicidins
chemical_list: D023181:Antimicrobial Cationic Peptides; D007074:Immunoglobulin G; D018950:Lipopolysaccharide Receptors; D044042:Receptors, Formyl Peptide; D017452:Receptors, IgG; C493487:Tlr4 protein, mouse; D051197:Toll-Like Receptor 4; C481578:formyl peptide receptor 2, mouse; D054804:Cathelicidins
keywords: FcγR; TLR; cathelicidin; infection; innate immunity