neutrophil
Meaning of neutrophil: Short lived by design: these cells are produced in vast numbers, survive briefly and die where they fight, which is what pus is.
Definition of neutrophil
A neutrophil is the most common white blood cell in adult blood and the immune system's first responder. It circulates ready for use, reaches a site of infection or injury within hours, and destroys bacteria and fungi by engulfing them and digesting them with enzymes stored in granules packed inside the cell.
How does a neutrophil reach the trouble?
Damaged tissue and invading bacteria release signaling molecules that diffuse into nearby vessels. Neutrophils flowing past detect them, slow down and roll along the vessel wall, stick to it, then squeeze between the cells lining it and crawl through the tissue toward the strongest signal. The redness, heat and swelling of inflammation come largely from the vessel changes that make this possible. The whole sequence takes hours, which is why neutrophils dominate the first day of a bacterial infection while slower, more specific cells are still being recruited.
How does it kill?
The main method is swallowing the organism whole. The cell wraps around the microbe, encloses it in a bubble, and fuses that bubble with granules containing digestive enzymes and antimicrobial proteins. It also generates reactive oxygen compounds inside the same compartment, a burst of chemistry that is lethal at close range. Two other methods carry more collateral cost: releasing granule contents into the surrounding tissue, and casting out a web of the cell's own DNA studded with enzymes, which traps organisms outside the cell. Both damage nearby tissue as well, and a neutrophil generally dies in the process. Accumulated dead neutrophils, digested tissue and fluid are what make up pus.
What does the count mean?
| Finding on a blood count | What it can indicate |
|---|---|
| Raised neutrophil count | Bacterial infection, tissue injury or inflammation; also physical stress, corticosteroid treatment and, rarely, a marrow disorder |
| Increased immature forms | The marrow releasing cells early to keep pace with demand, described as a left shift |
| Low count, or neutropenia | Reduced production, as after chemotherapy, or faster destruction; susceptibility to bacterial and fungal infection rises as the count falls |
The number is read as part of a full blood cell count and alongside the clinical picture, since the same value carries different weight in different situations.
Used in a sentence
The complete blood count showed an elevated neutrophil count consistent with an acute bacterial infection.
Good to know
A high neutrophil count often points toward bacterial infection or acute inflammation, while a low count, called neutropenia, can increase susceptibility to infection regardless of the underlying cause.
Word origin
Where “neutrophil” comes from
Formed from neutro-, from Latin neuter, meaning neither, and -phil, from Greek philos, meaning loving or having an affinity for, describing how the cell's granules take up neutral laboratory stains rather than strongly acidic or basic ones.