Neutrophil !

Cell

The most common white blood cell: a short-lived first responder that rushes to bacteria, eats them and dies, forming pus.

Updated 2026-11-01

What it is

Neutrophils are granulocytes with a nucleus of several lobes and fine pale granules. They are the most numerous white cells in blood and the first to arrive at acute inflammation, where they engulf and kill bacteria and fungi. Too few neutrophils leave a person open to severe bacterial and fungal infection; too many usually signal infection, inflammation or stress.

Key facts

Origin: myeloid progenitor in the bone marrow; production is boosted by granulocyte colony-stimulating factor.
Lifespan: hours in the blood and a few days in tissue; they die by apoptosis or at the infection site.
Dead neutrophils, debris and fluid form pus.

Function

Roll, stick and squeeze out of venules toward chemical signals (chemotaxis).
Recognize microbes directly or after opsonization by antibody or complement.
Destroy them inside the phagosome with granule enzymes and oxidants.

Markers

CD15
CD16
CD11b/CD18 (integrin)
Myeloperoxidase

Clinical notes

Neutropenia: risk of serious bacterial and fungal infection; fever with neutropenia is an emergency (chemotherapy, aplastic anemia, some drugs, severe sepsis).
Neutrophilia: bacterial infection, inflammation, burns, acute stress, glucocorticoids, smoking and some leukemias.
Chronic granulomatous disease: no NADPH oxidase, so catalase-positive bacteria and fungi cause recurrent abscesses.
Leukocyte adhesion deficiency (CD18): high blood neutrophils that cannot leave vessels, no pus, delayed separation of the umbilical cord.

In the lab

Complete blood count with differential gives the absolute neutrophil count.
Blood smear: band forms, toxic granulation, hypersegmentation.
Dihydrorhodamine flow test for chronic granulomatous disease.

Test yourself

Think of the answer, then tap the question to see it.

Which white cell is the first to arrive at a site of acute bacterial inflammation?

The neutrophil.

What does a left shift on the smear mean?

More immature band neutrophils in the blood, typically during an acute bacterial infection.

Which vitamin deficiencies cause hypersegmented neutrophils?

Vitamin B12 and folate deficiency (megaloblastic anemia).

Why is fever in a patient with neutropenia an emergency?

Without enough neutrophils, bacterial and fungal infections can spread quickly and become life-threatening.

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← All of immunology

Educational content on the immune system; not a treatment or individual vaccination guide and no substitute for a health professional's advice. No doses are given.

Sources: 18.4 Leukocytes and Platelets (OpenStax, Rice University (Anatomy and Physiology 2e), 2022); Neutrophils (British Society for Immunology, 2024); Blood differential test (MedlinePlus, U.S. National Library of Medicine, 2024); Neutropenia - infants (MedlinePlus, U.S. National Library of Medicine, 2024).

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Representative model, for educational purposes only.