Macrophage
Say it: MAK-roh-fayj
A macrophage is a large white blood cell that engulfs and digests microbes, dead cells and debris, and signals other immune cells to act.
Also: macrophages
Definition
What is a macrophage?
A macrophage is a large phagocyte, a cell that eats particles by wrapping its membrane around them. Most macrophages begin as monocytes circulating in the blood; when a monocyte leaves the bloodstream and enters a tissue, it matures into a macrophage. Some macrophages settle for long periods in particular organs, such as the lungs and liver, where they stand guard.
Macrophages are part of innate immunity. Receptors on their surface, including Toll-like receptors, detect molecular patterns shared by many microbes. After swallowing a microbe, the macrophage holds it in a vesicle that fuses with lysosomes, whose enzymes break it down. Macrophages also release cytokines that start inflammation and call in other white blood cells. In addition, they place fragments of what they have eaten on MHC class II molecules, acting as antigen-presenting cells that help switch on helper T cells. In this way they link innate and adaptive immunity.
Beyond fighting infection, macrophages clear away dead and dying cells, including those removed by apoptosis, and they mop up pus and debris so that damaged tissue can be repaired.
Word parts
Where does the word “macrophage” come from?
- macro-
- largeGreek makros
- -phage
- eaterGreek phagein, to eat
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Terms that go with it
- Innate immunityInnate immunity is the inborn, fast-acting set of body defenses that reacts to any invader in the same general way, with no prior exposure needed.
- White blood cellA white blood cell, or leukocyte, is any of the nucleated immune cells in blood that defend the body against infection and clear away debris.
- InflammationInflammation is the body's protective response to infection or injury, in which leaky, widened blood vessels bring immune cells and fluid to the site.
- CytokineA cytokine is a small signaling protein released by cells, especially immune cells, that changes how other cells behave, grow or respond to infection.
- Major histocompatibility complexThe major histocompatibility complex is a set of genes whose proteins display protein fragments on cell surfaces so that T cells can inspect them.
- LysosomeA lysosome is a membrane-bound organelle filled with acidic digestive enzymes that break down worn-out cell parts, food particles and microbes.
Sources
Checked against
Written for biofideX in plain words, after checking these references:
- OpenStax Biology 2e, 42.1 Innate Immune Response
- NCI Dictionary of Cancer Terms: macrophage
- OpenStax Microbiology, 18.2 Major Histocompatibility Complexes and Antigen-Presenting Cells
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