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Neutrophil secretion products stimulate phagocytosis in macrophages
Author(s) -
Soehnlein Oliver,
Eriksson Einar E,
Lindbom Lennart
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.4.a704-a
Subject(s) - phagocytosis , secretion , chemotaxis , exocytosis , microbiology and biotechnology , macrophage , immune system , western blot , biology , monocyte , immunology , chemistry , receptor , in vitro , biochemistry , gene
Neutrophils (PMN) and monocyte‐derived macrophages (Mø) are the principle phagocytic cells in the response to bacterial infections. PMN are the first cells to emigrate into inflamed areas and are followed by monocytes, which differentiate into inflammatory Mø. It has been suggested that secretion products from PMN influence the function of other recruited immune cells. Here we study the effect of PMN secretion on Mø phagocytosis. Secretion from human PMN was obtained after treatment with fMLP or by antibody cross‐linking of beta2‐integrins (X‐link). Monocytic THP‐1 cells or Mø differentiated from human monocytes were treated with either of the secretions. Cells were subsequently incubated with fluorescent Staphylococcus aureus and the number of phagocytosed bacteria per cell was quantified by fluorescence microscopy. Both fMLP and X‐link secretions enhanced phagocytosis compared to baseline in both cell types. Treatment with fMLP secretion evoked stronger phagocytosis compared to X‐link secretion in THP‐1 cells whereas X‐link supernatant had a more robust effect on human Mø, indicating distinct functional activity of the respective secretions. Western blot analysis revealed that fMLP activation of PMN results in exocytosis of secretory vesicles and tertiary granules, whereas cross‐linking of beta2‐integrins mobilises all types of granules and vesicles. Our results indicate that PMN secretion products activate monocytes and Mø to phagocytose bacteria. This may contribute to host defense in bacterial infections and could be of potential use in antimicrobial therapy. This study was supported by a grant from the Swedish Research Council.