Definition of neutrophils, Low, High, Function and, Structure

Definition of neutrophils

Neutrophils are a type of white blood cell with multilobed nuclei and stainable cytoplasmic granules.

  • These are the most abundant granulocytes, occupying about 40-60% of the total number of white blood cells in the blood.
  • Neutrophils, like all other blood cells, are formed from stem cells in the bone marrow.
  • After differentiation in the bone marrow, neutrophils are released into the peripheral blood and circulate 7 to 10 hours before migrating to the tissues, where they have a shelf life of just a few days.
  • These are highly mobile, allowing them to quickly enter and exit cells and tissues during infection.
  • Neutrophils are divided into two groups; neutrophil killers and neutrophil cagers.
  • Neutrophils are in the front line of attack during an immune response and are considered part of the innate immune system.
Definition of neutrophils, Low, High, Function and, Structure

Neutrophil Structure

  • Neutrophils are mostly circular, 12-15 µm in size (average human size is 8 µm).
  • Their form changes to ameboid once they are activated so that they can extend their pseudopodia to attack the invaders.
  • These are the smallest granulocytes with a characteristic multilobed nucleus with 3-5 lobes linked by a thin chain of genetic material.
  • The nucleolus is present in young neutrophils but is lost as the neutrophil matures.
  • The cytoplasm of neutrophils has a large number of purple granules, called azurophilic or primary granules that have microbicidal activity.
  • Also, secondary granules are found in the cytoplasm containing lysozyme, collagenase, and other enzymes.
  • Other cytoplasmic organelles such as mitochondria, the Golgi complex appear in moderation, and the endoplasmic reticulum is completely absent.
Definition of neutrophils, Low, High, Function and, Structure

Absolute Neutrophil Count

  • Absolute Neutrophil Count (ANC) is the test to measure the amount of neutrophils and other granulocytes (collectively called polymorphonuclear cells) present in a blood sample.
  • This test generally detects the total number of white blood cells that include both mature and immature neutrophils.
  • The blood count of neutrophils breaks neutrophils into two categories such as mature or segmented neutrophils and immature neutrophils or bands.
  • Neutrophil count is commonly performed to detect abnormalities related to the increase or decrease in the number of neutrophils.
  • The abnormal neutrophil count is often associated with various medical conditions, making this test an essential part of the laboratory examination of many diseases.
  • The formula for calculating the absolute neutrophil count is given below:

ANC= (Total WBC) x [(% of neutrophils + % of bands) ÷ 100]

&

ANC= Absolute mature neutrophils + absolute immature neutrophils

  • This test is done to detect the presence of different organisms in the bloodstream and also to detect if the immune system is working properly.
  • ANC is usually performed as part of the complete blood count to measure the count of different blood cells.

Neutrophils normal range

The number of neutrophils in the blood can vary from person to person, as it is affected by various factors such as age and the environment. However, the following is considered for the normal range of neutrophil counts.

In terms of cell count:

  • The normal range of ANC counts in adults: 1500-8000 cells / mm3.
  • The normal range of mature / segmented neutrophils: 2500-6000 cells / mm3.
  • The normal range of immature neutrophils: 0-500 cells / mm3.

In terms of WBC percentage:

  • The normal range of ANC count in adults: 40-45%
  • The normal range of mature/segmented neutrophils: 40-60%
  • The normal range of immature neutrophils: 0-5%

Neutrophils low 

When the level of neutrophils is less than 1500 cells / mm3 of blood volume, it is considered a low level of neutrophils.

This condition is also called neutropenia. Mild neutropenia is the condition where the levels are between 1000-1500 cells / mm3. When the levels are between 500-100 cells / mm3, it is called moderate neutropenia. When the levels are below 500 cells / mm3, it is severe neutropenia.

The low neutrophil count is often seen with medication intake, but it can also be a sign of some other factors or diseases.

Causes of low neutrophil count

The Causes of low neutrophil count:

  • The most important cause of low neutrophil count is the intake of medications, especially those taken during chemotherapy.
  • A weakened immune system due to some underlying diseases like AIDS, tuberculosis, and hepatitis also causes low levels of neutrophils.
  • Similarly, other conditions such as cancer and related bone marrow diseases also result in a low neutrophil count.
  • Another cause of neutropenia is a deficiency of vitamin B12 and other minerals.
  • Autoimmune diseases like Crohn’s disease, lupus, and rheumatoid arthritis also cause a decrease in the neutrophil count.

High neutrophils

When the neutrophil level is greater than 8000 cells / mm3, a high level of neutrophils is considered.

This condition is called neutrophilia. Neutrophilia can range from mild and occasional neutrophilia to a more serious condition, often called neutrophil leukocytosis.

Because neutrophils are part of the immune system, an increase in a neutrophil count is mainly caused by a bacterial infection, but elevated levels are also caused by other factors.

Causes of high neutrophil count

The causes of the high neutrophil count are:

  • The most common cause of neutrophilia is a bacterial infection, especially pyogenic infections that cause inflammation.
  • Additionally, an increase in the neutrophil count is also observed during inflammation, usually after heart attacks or burns.
  • An increased concentration of the hormones cortisol and adrenaline and the ingestion of some medications such as prednisone also cause more neutrophils to enter the bloodstream.
  • Neutrophilia is also seen as a result of malignancy like leukemia.
  • Surgical procedures, including splenectomy and appendicitis, are also known to increase neutrophil counts.

Neutrophil functions

  • Neutrophils are the most abundant granulocytes that makeup about 40% of white blood cells and 60% of immune cells in the blood.
  • Neutrophils are the first to respond to infection, phagocytizing bacteria into phagosomes before hydrolyzing and destroying them.
  • These cells also secrete a variety of proteins that have antimicrobial effects, as well as a potential for tissue remodeling.
  • Neutrophils have a short lifespan, and therefore destroy themselves during degradation by foreign invaders. New neutrophils are continually produced in the bone marrow.
  • Neutrophils from another subpopulation, cager neutrophils, perform a transport function of delivering foreign particles to the target site for the action of killer neutrophils.
Definition of neutrophils, Low, High, Function and, Structure

Definition of neutrophils, Low, High, Function and, Structure

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Definition of neutrophils, Low, High, Function and, Structure

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