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Updated: Aug 8, 2025
Investigation of Macrophage Polarization Using Bone Marrow Derived Macrophages
Published on: June 23, 2013
Ready, STAT3, Go! Bacteria in the race for M2 macrophage polarisation
Ioanna Panagi1, Teresa Lm Thurston1
1MRC Centre for Molecular Bacteriology and Infection, Department of Infectious Disease, Imperial College London, SW7 2AZ, UK.
Abstract:
Despite macrophages representing professional immune cells that are integral to the host defences against microbial threats, several intracellular bacteria not only infect, but survive, replicate and often persist in these cells. This is perhaps possible because not all macrophages are the same. Instead, macrophages are loosely divided into two classes: the M1 'classically activated' pro-inflammatory subset and the M2 'alternatively activated' cells that are generally anti-inflammatory and infection-permissive. In this review, we summarise recent findings explaining how several intracellular pathogens, often using secreted effectors, rewire host circuitry in favour of an anti-inflammatory niche. A common theme is the phosphorylation and activation of the signal transducer and activator of transcription-3 (STAT3) transcription factor. We describe and compare the diverse mechanisms employed and reflect how such non-canonical processes may have evolved to circumvent regulation by the host, providing a potent means by which different pathogens manipulate the cells they infect.
Insights
Intracellular bacteria survive within macrophages by manipulating host defenses. Pathogens activate the signal transducer and activator of transcription-3 (STAT3) to create an anti-inflammatory environment, promoting infection.
Area of Science:
- Immunology
- Microbiology
- Cell Biology
Background:
- Macrophages are key immune cells, but some intracellular bacteria thrive within them.
- Macrophages exist in different states, including M1 (pro-inflammatory) and M2 (anti-inflammatory, infection-permissive).
Purpose of the Study:
- To review how intracellular pathogens exploit macrophage subsets for survival and replication.
- To highlight common mechanisms pathogens use to establish intracellular niches.
Main Methods:
- Literature review of recent findings on host-pathogen interactions.
- Analysis of molecular mechanisms employed by intracellular bacteria.
Main Results:
- Intracellular pathogens rewire host cell circuitry to favor anti-inflammatory conditions.
- A frequent strategy involves the activation of the STAT3 signaling pathway.
- Pathogens utilize secreted effectors to manipulate host cell functions.
Conclusions:
- STAT3 activation is a common mechanism for pathogens to create permissive intracellular niches.
- These non-canonical pathways allow pathogens to evade host immune responses.
- Understanding these manipulations offers insights into host-pathogen co-evolution.
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