Neutrophils

Generality

Neutrophils are the most numerous white blood cells found in circulating blood. These cells protect the body from foreign agents, especially infectious ones, exercising different actions in defense of the organism . These interventions are concatenated and perfectly integrated with those of the monocyte-macrophage system and lymphocytes.

To proceed with the removal of pathogenic microorganisms, neutrophils:

• They reach the place of infection with active movements ( chemotaxis );
• They take contact and ingest the foreign agent ( phagocytosis );
• They proceed to the digestion of the phagocytosed ( microbicide activity ).

• to enzymes contained in their primary and secondary granules,
• to the particular structure of the cytoplasmic membrane
• in the presence of receptors for immunoglobulins G (IgG antibodies) and for complement proteins.

Under normal conditions, mature neutrophils migrate into the blood stream, where they remain for a rather short time (6-12 hours), depending on various needs of the body (fever, stress, infections, etc.). After this period, these white blood cells go to confine themselves in the tissues, where they remain for a few days, before dying.

Neutrophil alterations may involve excess or deficient numerical changes and may be primitive or acquired.

• Primitive forms can result from genetic mutations that cause a defect in the production, distribution or functionality of neutrophils.
• The acquired or secondary forms can be consequent to infections, parasitosis, necrosis and tissue damage, allergic manifestations and intake of certain drugs.

What are

Neutrophils are the most abundant white blood cells in the blood. Their main characteristic is the segmented shape of the nucleus, consisting of three to five lobes, joined by thin bridges of nucleic material (see figure).

The number of lobes increases with the age of the cell: as soon as it is introduced into the blood it has only two lobes, which can reach five in old age. Due to this particular nuclear conformation, neutrophils are called polymorphonuclear leukocytes .

Produced in the bone marrow like all other blood cells, neutrophils have a remarkable phage activity, which allows them to incorporate and kill five to twenty bacteria over a lifetime (which lasts an average of one or two days).

This action, similar to that of tissue macrophages, occurs above all in the blood; if the need arises, neutrophils are however able to migrate to extravascular sites damaged or affected by an infection.

The digestion of cellular or molecular antigens occurs through the release of lytic enzymes contained in their granules. It is therefore not a coincidence that the main white blood cells in disintegration found in the pus are precisely the neutrophils.

In addition to absorbing and digesting microorganisms, debris and senescent cells, infected or transformed, neutrophils release particular chemical substances, including pyrogens (responsible for fever) and chemical mediators of the inflammatory response.

The neutrophils themselves, due to their marked amoeboid activity, are attracted by a series of chemotactic factors at the site of inflammation.

Because they measure themselves

The analysis of neutrophils is part of the blood count with a leukocyte formula, performed as part of routine examinations to assess the patient's state of health.

The count and morphological analysis of neutrophils provide support in the diagnosis of certain types of conditions and diseases, which can affect this type of white blood cells, such as:

• Infections caused by bacteria, viruses, fungi or parasites;
• Inflammation;
• Allergies;
• Neoplasms;
• Conditions affecting production and survival (immune disorders, autoimmune diseases, drug or chemical poisoning, etc.).

The evaluation of neutrophils also allows:

• Monitor the progression of specific diseases;
• Check the body's response to various treatments, especially if the therapeutic protocol (such as radiotherapy and chemotherapy) tends to damage white blood cells and / or compromises bone marrow function.

Normal values

Under normal conditions, neutrophils make up 40-75% of peripheral blood nucleated cells.

Values ​​that should be found outside the range - between 1, 500 and 7, 000 per cubic millimeter (mm3) - must be considered anomalous.

Note : reference values ​​related to neutrophils can change according to age, sex and instrumentation used in the analysis laboratory. For this reason, it is preferable to consult the ranges listed directly on the report. It should also be remembered that the results of the analyzes must be assessed as a whole by the general practitioner who knows the patient's medical history.

High Neutrophils - Causes

The number of circulating neutrophils varies considerably in the population and is around 4, 000 cells per mm3 of blood (the normal range is between 1, 500 and 7, 000 per mm3).

We talk about NEUTROPHILIA when the number of circulating neutrophils exceeds 8-9, 000 per mm3; this condition is found in a wide variety of situations (see table).

High neutrophils: Possible causes

• Physiological stimuli (moderate and temporary neutrophilia):
• Birth;
• Parto;
• Menstrual period;
• Muscle activity;
• Temperature changes;
• Stress;
• Ache.
• Infections: more often bacterial, localized or generalized (abscess, appendicitis, tonsillitis, septicemia etc.), but also fungal, viral and parasitic infections.
• inflammation:
• Surgical interventions;
• collagen;
• Trauma;
• Tissue necrosis (burns, heart attack);
• Allergies and other inflammatory diseases.
• Drugs, hormones, poisoning: lead, mercury, lithium, benzene, carbon monoxide, corticosteroids, adrenaline and noradrenaline, heparin, endotoxins, insect poisons.
• Malignancies:
• Myeloproliferative diseases;
• Carcinomas (especially if with bone metastases);
• Lymphomas.
• blood disorders:
• Hemolysis or acute hemorrhage;
• Megaloblastic anemias in treatment;
• Post agranulocytosis.
• Various:
• Increased blood urea;
• Diabetic acidosis;
• Cigarette smoke;
• Idiopathic (familial) neutrophilia.

Low Neutrophils - Causes

In the presence of a reduced number of neutrophils in the blood we speak of NEUTROPENIA . The cause may be a genetic or acquired disease, such as aplastic anemia or some infections (typhoid, paratyphus and brucellosis). Neutropenia can also be the side effect of some drugs, especially anticancer chemotherapy.

In general, the problem can be upstream (reduced or altered synthesis at bone marrow level) or downstream (increased degeneration).

When neutrophils are low, the body is more susceptible to infections, particularly bacterial infections.

Leukopenia and granulocytopenia are often used as synonyms of neutropenia, but strictly speaking they are not exactly equivalent. In fact, leukopenia means a decrease in white blood cells and as such may also be due to deficits in other types of leukocytes, particularly lymphocytes; granulocytes, on the other hand, include - in addition to neutrophils - also eosinophils and basophils, although their contribution to the total count is modest.

Degree of neutropenia

• Mild neutropenia (1000-1500 / mm3): reduced risk of infection.
• Moderate neutropenia (500-1000 / mm3): moderate risk of infection.
• Severe neutropenia (<500mm3): severe risk of infection.

How to measure them

To establish the value of neutrophils, it is sufficient to undergo a blood count (complete blood count), complete with a leukocyte formula . A sample of blood from a vein in the arm, usually in the morning and fasting, is then taken from the patient.

Counting can be done automatically by electronic meters or by observation with an optical microscope (blood smear).

Preparation

To undergo blood sampling useful for the evaluation of neutrophils, it is necessary to abstain from food and drink for at least 8-10 hours. The general practitioner who prescribes the analyzes will still be able to provide useful information for the case.

Interpretation of Results

• Neutrophilia is the most common form of leukocytosis. The increase in the number of circulating neutrophils may depend on primitive alterations (caused by genetic mutations, as in the case, for example, of myeloproliferative disorders) and secondary ones. The main acquired causes of neutrophilia are represented by bacterial infections. A high value of neutrophils can also be found during necrosis and tissue damage (burns, traumas, etc.), intoxication and post-surgery.
• Neutropenia can depend on multiple causes, such as, for example, blood diseases, vitamin deficiencies, exposure to toxic agents, use of some drugs and immune reactions. There are also forms of a family nature (associated with genetic alterations) and idiopathic forms (whose cause is not known).