Antimicrobial peptide LL‐37 promotes bacterial phagocytosis by human macrophages. Issue 6 (1st June 2014)

• Record Type: Journal Article
• Authors: Wan, Min; van der Does, Anne M.; Tang, Xiao; Lindbom, Lennart; Agerberth, Birgitta; Haeggström, Jesper Z.
• Is Part Of: Journal of leukocyte biology. Volume 95:Issue 6(2014)
• Page Start: 971
• Page End: 981
• Publication Date: 2014-06-01
• Subjects: cathelicidin -- FcγR -- TLR -- innate immunity -- infection; Leucocytes -- Periodicals; Reticulo-endothelial system -- Periodicals; 571.96
• DOI: 10.1189/jlb.0513304
• Languages: English
• ISSNs: 0741-5400

Abstract

Abstract : Regulation of bacterial phagocytosis of human macrophages by antimicrobial peptide LL‐37, and its potential mechanisms. 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.