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Updated: May 11, 2025

Alveolar Macrophage Phagocytosis and Bacteria Clearance in Mice
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Bacterial pneumonia induces senescence in resident alveolar macrophages that are outcompeted by monocytes

Jinjing Zhang1, Tao Wang1, Yanling Wang1

  • 1Institute of Immunology and Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou 310058, China.

Cell Reports
|April 18, 2025
PubMed

Insights

Pulmonary bacterial infection causes lung macrophages to be replaced by monocyte-derived cells. Tissue-resident macrophages recover but are outcompeted, leading to altered immune responses.

Area of Science:

  • Immunology
  • Pulmonology
  • Microbiology

Background:

  • Alveolar macrophages (AMs) are crucial for lung health and immunity.
  • The replacement of embryonic-derived tissue-resident AMs (TRAMs) by monocyte-derived AMs (MoAMs) impacts lung function and disease susceptibility.
  • The mechanisms driving AM turnover are not fully understood.

Purpose of the Study:

  • To investigate the mechanisms of AM turnover during pulmonary bacterial infection.
  • To understand the functional consequences of AM replacement on host immunity.

Main Methods:

  • Utilized a mouse model of Streptococcus pneumoniae (S.P.) infection.
  • Analyzed AM populations and their functional states post-infection.

Main Results:

  • S.P. infection induced recruitment and differentiation of MoAMs, which became dominant in the post-infectious AM population.
  • TRAMs recovered in number post-infection but exhibited cellular senescence and reduced proliferation.
  • Senescent TRAMs were outcompeted by MoAMs in a competitive environment.

Conclusions:

  • Pulmonary bacterial infection triggers AM turnover, driven by MoAMs outcompeting senescent TRAMs.
  • This AM replacement reshapes AM functionality and may alter host susceptibility to respiratory diseases.
  • The findings provide novel insights into AM dynamics during lung infections.
Keywords:
CP: Immunologyalveolar macrophagesbacterial pneumoniamonocytesrespiratory mucosal immunologysenescence

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