Innate immunity
Say it: ih-NAYT ih-MYOO-nih-tee
Innate 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.
Also: innate immune system, nonspecific immunity, innate immune response
Definition
What is innate immunity?
Innate immunity is the part of the immune system that is present from birth and ready to act within minutes to hours of an infection. It does not need to learn a particular microbe first, and it responds in much the same way every time. Its first line is made of physical and chemical barriers: skin, mucus, cilia that sweep the airways, tears, and stomach acid.
When a microbe gets past these barriers, innate cells and proteins take over. Phagocytes such as neutrophils and macrophages carry pattern recognition receptors that detect molecular features common to many microbes, then engulf and digest them. Natural killer cells destroy infected cells, complement proteins coat or puncture microbes, interferons warn nearby cells that a virus is present, and inflammation and fever bring more defenders to the site.
Innate defenses often clear an infection on their own. When they cannot, dendritic cells and other antigen-presenting cells carry pieces of the microbe to T cells and switch on adaptive immunity, the slower, more targeted response that also leaves lasting memory.
Word parts
Where does the term “innate immunity” come from?
- innate
- inbornLatin innatus, from in- + nasci, to be born
- immunity
- exemption, protectionLatin immunis, exempt
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Terms that go with it
- Adaptive immunityAdaptive immunity is the branch of the immune system that learns to recognize specific antigens and remembers them, so it responds faster next time.
- MacrophageA macrophage is a large white blood cell that engulfs and digests microbes, dead cells and debris, and signals other immune cells to act.
- Complement systemThe complement system is a set of blood proteins that switch each other on in a cascade to tag microbes, drive inflammation and punch holes in them.
- 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.
- 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.
Sources
Checked against
Written for biofideX in plain words, after checking these references:
- OpenStax Biology 2e, 42.1 Innate Immune Response
- MedlinePlus Medical Encyclopedia: Immune response
- OpenStax Microbiology, 17.2 Chemical Defenses
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