Direct neutrophil and T cell contact with macrophages induces release of phagosomally processed PAMPs via eructophagy

Area of Science:

• Immunology
• Cell Biology
• Molecular Biology

Background:

• Macrophages clear debris and microbes via phagocytosis, orchestrating inflammation.
• Pathogen- and damage-associated molecular patterns (PAMPs and DAMPs) are typically secreted as soluble mediators.
• Eructophagy, a proposed mechanism, involves macrophages releasing processed PAMPs/DAMPs to activate other leukocytes.

Purpose of the Study:

• To investigate the induction of eructophagy in macrophages.
• To determine the role of physical interactions with neutrophils and T cells in eructophagy.
• To elucidate the molecular mechanisms underlying ICAM1/LFA1-mediated eructophagy.

Main Methods:

• Co-culture systems of macrophages with neutrophils and T cells.
• Immunofluorescence microscopy to visualize cellular interactions and phagolysosome content.
• Western blotting and kinase assays to assess Lyn kinase activity.
• Flow cytometry to analyze leukocyte activation markers.

Main Results:

• Eructophagy in macrophages is significantly induced by physical interactions with neutrophils and T cells.
• This interaction is mediated by ICAM1 on macrophages and lymphocyte function-associated antigen 1 (LFA1) on neutrophils and T cells.
• ICAM1 activation alone is sufficient to trigger eructophagy, dependent on Lyn kinase activity.

Conclusions:

• Neutrophils and T cells induce macrophage eructophagy via ICAM1/LFA1 interactions.
• This process facilitates the release of PAMPs/DAMPs from macrophages, potentially influencing leukocyte activation.
• Eructophagy represents a novel mechanism for intercellular communication and immune regulation in inflammatory settings.