Phagocytosis imprints heterogeneity in tissue-resident macrophages

Area of Science:

• Immunology
• Cell Biology
• Tissue Homeostasis

Background:

• Tissue-resident macrophages possess diverse phenotypes and functions influenced by their local microenvironment.
• Phagocytosis, a key macrophage function for cellular waste disposal, remains poorly understood in vivo.
• Understanding macrophage heterogeneity is crucial for tissue homeostasis and immune regulation.

Purpose of the Study:

• To investigate the mechanisms and consequences of phagocytosis by tissue-resident macrophages in vivo.
• To identify tissue-specific differences in macrophage phagocytic activity.
• To determine the impact of phagocytosis on macrophage phenotype and tissue homeostasis.

Main Methods:

• Utilized a parabiosis-based strategy to isolate and study phagocytosing macrophages from multiple tissues.
• Analyzed receptor repertoires, opsonins, and transcription factors involved in tissue-specific phagocytosis.
• Assessed the phenotypic and functional changes in macrophages following phagocytosis.

Main Results:

• Phagocytosis by tissue-resident macrophages is circadianally regulated.
• Distinct molecular mechanisms govern phagocytosis in macrophages from different tissues.
• Phagocytosis induces an anti-inflammatory macrophage phenotype, characterized by CD206 expression and reduced Il1b.
• Phagocytic macrophages contribute to maintaining tissue homeostasis.

Conclusions:

• Phagocytosis is a significant driver of macrophage heterogeneity, alongside tissue-specific factors.
• The anti-inflammatory profile induced by phagocytosis is critical for tissue homeostasis.
• This study provides new insights into the dynamic regulation of macrophage function in vivo.