The inside of a vein showing white blood cells or leukocytes. Credit: Dr. Richard Kessel & Dr. Gene Shih / Getty Images

Neutrophils - Definition

Neutrophils are a common type of white blood cell. Neutrophils respond to infection and attack bacteria and other foreign invaders directly. They are phagocytes that eat the invading organisms and kill them. They produced in your bone marrow and circulate in the blood, Neutrophils are abundant, they make up about 50% to 75% of your total white blood cells. 

  • Pronunciation: newt-row-fils
  • Also Known As: pus cells, Neu, PMN, polys, neutrophil granulocytes, polymorphonuclear neutrophils, bands, segs, white blood cells

What Do Neutrophils Do?

Neutrophils are the first type of immune cell to respond to and arrive at the site of infection, often within an hour. Neutrophils will respond to infection inside the body, but also on the surface, as in the case of skin infections. Pus, which is one visible sign of a skin infection, contains mainly dead neutrophils, bacteria, and cells. Pus can form internally, as well, when there is an injury or abscess inside the body.

Neutrophils are part of the innate immune system, which means that they can "non-specifically" destroy any invaders that they encounter in the body, such as bacteria and parasites. Non-specifically means that neutrophils do not have to recognize the invader specifically, but instead simply recognize the invader as something that should not be present in the body and should be destroyed.

What Tests are Done for Neutrophils?

Neutrophils are counted as part of the CBC complete blood count test and the Diff, or white blood cell differential examination. These tests may be done as screening tests for general health or ordered to assist in diagnosis of disease or monitoring of ongoing conditions or treatment.

The absolute neutrophil count has a reference range of 1800-7800 per microliter. Their mean percentage of all white cells is 56%. A high count may be due to bacterial infection, inflammation, trauma and some leukemias. A low count may be due to sepsis, reaction to chemotherapy or radiation treatment, and in autoimmune disorders.

The test is performed by drawing your blood in a tube that has an anticoagulant to keep it liquid. The blood is analyzed in a cell counter that can identify different types of cells. The differential count may be automated or it may be performed on a blood smear.

The instrument or the laboratory technologist counts the percentage of each type of white cell. In addition, they classify the neutrophils as to whether they have segmented nuclei, showing a mature neutrophil, or a band nuclei, showing it is a young neutrophil. When there is a larger than normal percentage of bands, it indicates an active response to an infection.

Neutrophils in Cancer Treatment

The results of the absolute neutrophil count (ANC), are routinely checked during cancer treatment to determine how the immune system is responding to treatment. When ANC is low, this is called neutropenia. If ANC drops below about 500 cells per microliter, the risk of infection increases and your doctor may prescribe medications to bring ANC back into a normal range and temporarily offer antibiotics to prevent serious infections.


Complete Blood Count, Lab Tests Online, November 9, 2015. American Association for Clinical Chemistry.

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