Neutrophil
Most abundant white blood cell, key in innate immunity.
Neutrophils are a type of phagocytic white blood cell and part of innate immunity. They form the most abundant type of granulocytes and make up 40% to 70% of all white blood cells in humans. Their functions vary in different animals; in humans they participate in processes such as sterile inflammation, tissue repair, and cancer, and exhibit coordinated collective behavior. They are also known as neutrocytes, heterophils, or polymorphonuclear leukocytes.
- field
- Immunology, Hematology
- known_for
- First responders in acute inflammation; predominant cells in pus; phagocytic activity against bacteria
- normal_range
- 2.5–7.5 × 10⁹/L in human blood
- diameter
- 12–15 μm (adhered); 8.85 μm (in suspension)
Lore & Background
Neutrophils are formed from stem cells in the bone marrow and differentiated into subpopulations of neutrophil-killers and neutrophil-cagers. They are short-lived and highly mobile, able to enter parts of tissue where other cells or molecules cannot. Neutrophils may be subdivided into segmented neutrophils and banded neutrophils (or bands). They form part of the polymorphonuclear cells family (PMNs) together with basophils and eosinophils. The name neutrophil derives from staining characteristics on hematoxylin and eosin (H&E) preparations: whereas basophilic white blood cells stain dark blue and eosinophilic white blood cells stain bright red, neutrophils stain a neutral pink. Normally, neutrophils contain a nucleus divided into 2–5 lobes.
Reader's Guide
Neutrophils are central to the acute phase of inflammation, particularly in response to bacterial infection, environmental exposure, and some cancers. They are among the first inflammatory cells to migrate toward the site of injury, following chemical signals such as interleukin-8 (IL-8), C5a, fMLP, leukotriene B4, and hydrogen peroxide in a process called chemotaxis. They are the predominant cells in pus, accounting for its whitish-to-yellowish appearance. Neutrophils not only combat infection but also contribute to pain in the acute period by releasing pro-inflammatory cytokines and other mediators that sensitize nociceptors. However, due to some pathogens being indigestible, they may not resolve certain infections without assistance from other immune cells. Their short lifespan is hypothesized to be an evolutionary adaptation that minimizes propagation of pathogens that parasitize phagocytes and limits host tissue damage during inflammation.
Did You Know?
- Up to 17% of female human neutrophil nuclei have a drumstick-shaped appendage containing the inactivated X chromosome.
- The capacity of neutrophils to engulf bacteria is reduced when simple sugars like glucose, fructose, sucrose, honey, and orange juice are ingested, while fasting strengthens this capacity.
- Neutrophils preferentially engulf and kill beta-1,6-glucan targets compared to beta-1,3-glucan targets.
- The distribution ratio of neutrophils in bone marrow, blood, and connective tissue is 28:1:25.
Frequently Asked Questions
Who is Neutrophil?
Neutrophil is the most abundant granulocyte in human blood, making up roughly 40–70% of all circulating white blood cells. It is a professional phagocyte within the innate immune system and goes by several aliases, including neutrocyte, heterophil, and polymorphonuclear leukocyte.
What are Neutrophil's powers or role?
Neutrophil serves as the body's first responder in acute inflammation, rapidly engulfing and killing bacteria through phagocytosis. Beyond direct pathogen destruction, it also participates in sterile inflammation, tissue repair, and cancer-related processes, and can exhibit coordinated collective behavior with neighboring cells.
Why is Neutrophil important?
As the predominant cell found in pus, Neutrophil is the frontline defender that prevents bacterial infections from spreading unchecked. Its rapid phagocytic response makes it indispensable to the body's immediate, nonspecific immune defense.
What are Neutrophil's key stats?
A normal human blood count for Neutrophil falls between 2.5 and 7.5 × 10⁹ cells per liter. The cell measures approximately 12–15 μm in diameter when adhered to a surface and about 8.85 μm while free in suspension.
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