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Published on: August 6, 2013
A microbial strategy to multiply in macrophages: the pregnant pause
Michele S Swanson1, Esteban Fernandez-Moreira, Esteban Fernandez-Moreia
1Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI 48109-0620, USA. mswanson@umich.edu
Abstract:
Humans live in harmony with much of the microbial world, thanks to a sophisticated immune system. As the first line of defense, macrophages engulf, digest, and display foreign material, then recruit specialists to eliminate potential threats. Yet infiltrators exist: certain fungi, viruses, parasites, and bacteria thrive within sentinel macrophages. By scrutinizing the life styles of these shrewd microbes, we can deduce how macrophages routinely mount an effective immune response. The bimorphic life cycles of three pathogens have dramatic consequences for phagosome traffic. In the transmissible state, Leishmania spp., Coxiella burnetii, and Legionella pneumophila block phagosome maturation; after a pregnant pause, replicative forms emerge and thrive in lysosomes.
Insights
Macrophages defend the body by engulfing pathogens. However, some microbes like Leishmania, Coxiella, and Legionella survive within macrophages by blocking phagosome maturation, allowing them to replicate.
Area of Science:
- Immunology
- Microbiology
- Cell Biology
Background:
- Macrophages are critical immune cells that engulf and digest pathogens.
- Certain microbial pathogens have evolved mechanisms to evade macrophage defenses.
- Understanding these evasion strategies is key to developing effective treatments.
Purpose of the Study:
- To investigate how specific pathogens interfere with macrophage functions.
- To elucidate the mechanisms by which microbes survive within macrophages.
- To understand the consequences of microbial life cycles on phagosome trafficking.
Main Methods:
- Studying the life cycles of three specific pathogens: Leishmania spp., Coxiella burnetii, and Legionella pneumophila.
- Analyzing phagosome maturation and trafficking within infected macrophages.
- Microscopic and cellular assays to observe pathogen-macrophage interactions.
Main Results:
- The transmissible forms of Leishmania spp., Coxiella burnetii, and Legionella pneumophila successfully block phagosome maturation.
- These pathogens pause within the phagosome before entering a replicative state.
- Replicative forms of these pathogens thrive within lysosomes, indicating successful evasion.
Conclusions:
- The bimorphic life cycles of these pathogens are crucial for their survival within macrophages.
- Pathogen-induced disruption of phagosome maturation is a key strategy for intracellular replication.
- Studying these microbial adaptations provides insights into macrophage immune responses.
