Neutrophils: Definition, Structure, Count, Range, Functions

Neutrophils Definition

  • Neutrophils are a type of white blood cells (leukocytes) that are an important part of the immune system and helps the body fight infections. 
  • Neutrophils are essentially clear in color and thus dyes are needed to make them visible under the microscope. 
  • Neutrophils have multilobed nuclei and cytoplasmic granules that may be stained.
  • These granulocytes are the most prevalent, making up between 50 and 80 percent of all the white blood cells in the blood.
Neutrophils and blood cells
Image Credit: National Cancer Institute
  • Similar to every other blood cell type, neutrophils are created in the body by the stem cells found in the bone marrow.
  • Following differentiating in the bone marrow, neutrophils are released into the peripheral circulation. There, they flow for 7 to 10 hours before migrating into the tissues, where they have a short lifetime of several days.
  • Due to their great motility, they may swiftly enter and exit infected cells and tissues.
  • Neutrophil killers and neutrophil cagers are the two categories that neutrophils fall into.
  • Neutrophils, which are regarded as a component of the innate immune system, are the first to be assaulted during an immunological response.

Neutrophil Structure

  • Most neutrophils are spherical and range in size from 9 to 15 mm.
  • Once triggered, they take on an amoeboid morphology that allows them to extend their pseudopodia and attack intruders.
  • These granulocytes are the smallest and contain a unique multi-lobed nucleus, having three to five lobes joined via a thin strand of genetic material.
  • When a neutrophil is young, it has a nucleolus, but as it becomes older it loses it.
  • The neutrophils’ cytoplasm is filled with many azurophilic or primary granules, which are purple in color and exhibit microbial activity.
  • In addition, lysozyme, collagenase, and other enzymes are located in secondary granules in the cytoplasm.
  • The endoplasmic reticulum is completely gone, as are other cytoplasmic organelles, including the mitochondria and Golgi complex.
Neutrophils function diagram
Image Credit: Frontiers in Physiology

Neutrophils Test / Absolute Neutrophil Count

  • An absolute neutrophil count is the phrase for the test used to estimate the quantity of polymorphonuclear cells, which include neutrophils and other granulocytes, in a blood sample (ANC).
  • Neutrophils, both mature and immature, are included in the total number of white blood cells that are often detected by this test.
  • The neutrophil blood count categorizes neutrophils into segmented or mature neutrophils as well as immature neutrophils or bands.
  • The neutrophil count is frequently performed to find anomalies connected to an increase or decrease in the neutrophil population.
  • This test is crucial for the laboratory analysis of many diseases, since the aberrant neutrophil count is frequently linked to a variety of ailments.
  • The following is the formula for calculating the absolute neutrophil count:

           ANC= Absolute mature neutrophils + absolute immature neutrophils

  • This test is carried out to find out if the immune system is functioning properly, as well as the presence of certain pathogens in the circulation.
  • ANC is often done as part of a full blood count to count the various blood cells.

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Neutrophils Normal Range

Neutrophils make up a significant portion of the blood, but can vary from person to person depending on factors including environment and age. However, the following neutrophil count range is thought to be typical.

In terms of cell count:

  • Adults’ ANC counts should be between 1500 and, 8000 cells per millimeter(mm)3.
  • 2500-6000 cells/mm3 is the typical range for mature, segmented neutrophils.
  • Immature neutrophils typically range from 0-500 cells per mm3.

In terms of the percentage of the WBC:

  • Adults should have an ANC count of between 40 and 45%.
  • The typical range of segmented or mature neutrophils is 40–60%.
  • 0-5% is the typical range for immature neutrophils.

Neutrophils Low (With Causes)

  • It is said to have a low neutrophil count when there are fewer than 1500 cells per milliliter of blood.
  • Neutropenia is another name for this illness. Mild neutropenia is defined as 1000–1500 cells/mm3 or lower levels. Moderate neutropenia is defined as 500 to 100 cells/mm3 or higher. Severe neutropenia results from cell counts below 500 cells/mm3 in the body.
  • Low neutrophil counts are frequently seen after taking medicine, but they might also indicate other conditions or illnesses.

The Causes of the Low Neutrophil Count Are:

  • The use of medications, particularly those taken during chemotherapy, is the main factor contributing to decreased neutrophil counts.
  • Low neutrophil counts can also result from an immune system that has been inhibited by conditions including AIDS, TB, and hepatitis.
  • Low neutrophil counts are also a symptom of other illnesses, including cancer and associated bone marrow disorders.
  • The absence of minerals and vitamin B12 is another factor that contributes to neutropenia.
  • The number of neutrophils also declines as a result of autoimmune conditions such as Crohn’s disease, lupus, and rheumatoid arthritis.

Neutrophil High (With Causes)

  • A high neutrophil level is defined as having more than 8000 cells/mm3 of neutrophils.
  • Neutrophilia is the name given to this disorder. Neutrophilia can range from a moderate, infrequent disorder to a more serious one known as neutrophil leukocytosis.
  • Since neutrophils are immune system cells, bacterial infections are the main cause of a rise in neutrophil count. However, other causes can also contribute to the elevated levels.

The Causes of the High Neutrophil Count Are:

  • An infection with bacteria, particularly pyogenic infections that induce inflammation, is the most frequent cause of neutrophilia.
  • Additionally, an elevated neutrophil count is seen with inflammation, typically following heart attacks or burns.
  • More neutrophils also enter the circulation as a result of a rise in the levels of the hormones cortisol and adrenaline, as well as the use of some medications like prednisone.
  • Additionally, neutrophilia can occur from cancer, such as leukemia.
  • It is also known that surgical operations, such as splenectomy and appendicitis, boost neutrophil count.

Neutrophils Functions

  • The majority of granulocytes, or neutrophils, comprise 60% of the immune cells and 40% of the white blood cells in the blood.
  • The initial defense against infection is provided by neutrophils, which phagocytose bacteria into phagosomes before hydrolyzing and eliminating them.
  • Additionally, a variety of proteins with potential for tissue remodeling and antibacterial actions are secreted by these cells.
  • Due to their short lifespan, neutrophils self-destruct when destroying foreign invaders. The bone marrow then constantly produces new neutrophils.
  • The cager neutrophils, a different subset of neutrophils, provide a transport role by bringing foreign particles to the place where killer neutrophils would act.


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