Monocytes

Generality

MONOCYTES are a type of white blood cells (or leukocytes) that play more roles in our immune system. Among these tasks stands the phagocytic capacity, whose activation processes are not only implicated in the classical defense against pathogens ( infections ), but also in the regulation of other physiological activities ( coagulation ) and / or pathological ( atherosclerosis ).

Monocytes originate in the bone marrow and travel through the bloodstream to the tissues of the whole organism, where they mature and differentiate into MACROPHAGES . Furthermore, monocytes and macrophages stimulate other cells of the immune system by releasing enzymes, complement proteins and other regulatory factors.

Monocytes can be evaluated with the leukocyte formula, a blood test that quantifies the number of white blood cells in a cubic millimeter of blood, also expressing the quantitative and percentage ratio of the various types of leukocytes.

What are

Monocytes are extraordinarily effective "scavengers", capable of absorbing and digesting substances and micro-organisms that could damage the body.

Monocytes are produced by the bone marrow and placed in the bloodstream, where they remain only for a few hours, before migrating to the tissues where their action is required. At this level, they increase in size, are enriched with lysosomes and differentiate into macrophages .

Like neutrophil granulocytes, macrophages belong to the phagocyte category; compared to the latter, they have a greater capacity to incorporate and digest large or heavy particles. Highly specialized macrophages are present in various tissues, where they take on particular names, such as histiocytes (skin), Kupffer cells (liver), osteoclasts (bones), microglia (brain) and reticulo-endothelial cells (spleen).

Monocytes are distinguished from other white blood cells by their large size and their oval or kidney-shaped nucleus.

Throughout life, macrophages are able to phagocytose and kill more than 100 bacteria by digestion; they also succeed in removing larger cells (such as aged red blood cells and necrotic neutrophils) and unwanted particles, including those of coal and asbestos.

Macrophages are not able to immediately recognize all foreign substances, some of which are attacked only after the antibodies are bound to them, highlighting the danger.

Macrophages are part of a class of leukocytes called class II MHC (antigen presenting cells); in practice, after having digested the foreign elements, they elaborate molecular fragments by inserting them on their cell membrane. These surface protein complexes are recognized by particular white blood cells, called T helper lymphocytes, which absorb the danger and increase the body's immune response.

Functions of monocytes - macrophages

• Phagocytosis and killing of numerous pathogens.
• Phagocytosis and removal of cell fragments or dead cells.
• Collaboration with T Helper lymphocytes in promoting the immune response.
• Synthesis of numerous proteins, including complement and coagulation factors, interferon, CSA, transferrin.

Because they measure themselves

The counting and morphological analysis of monocyte-macrophages allows for the screening or diagnosis of some diseases that can affect these types of white blood cells, such as infections, inflammations or conditions that affect production and survival.

Furthermore, the determination of monocytes allows to monitor the progression of specific pathologies and to control the body's response to various treatments (efficacy, preserved or altered bone marrow function, possible side effects of such therapies, etc.).

Normal values

Under normal conditions, monocytes make up 1-6% of peripheral blood nucleated cells (about 200-600 monocytes per microliter of blood).

Values ​​that should be found outside the range must be considered anomalous and direct the doctor to more thorough investigations. These must necessarily lead to establishing the nature of the disease, in order to intervene to support the immune system as soon as possible.

High Monocytes - Causes

Due to the short stay times (about eight hours), monocytes are not very abundant in the blood, where they represent about 1-6% of all white blood cells. The permanence of macrophages at tissue level, where they can survive for months or even years, is decidedly longer lasting.

The pathological increase in the blood concentration of monocytes is defined as monocytosis and characterizes a long series of diseases.

High monocytes: the causes

• Some infectious diseases: tuberculosis, brucellosis, typhoid fever, subacute bacterial endocarditis, syphilis, malaria.
• Convalescence of acute infections.
• Pre-leukemic states
• Haematological diseases: chronic monocytic leukemia, myeloproliferative diseases, haemolytic anemias, neutropenia, lymphomas.
• Gastrointestinal affections: ulcerative colitis, regional enteritis, sprue.
• Collagenopathies: systemic lupus erythematosus, rheumatoid arthritis, myositis, polyarteritis nodosa.
• Miscellaneous: sarcoidosis, post-splenectomy.

Bass monocytes - Causes

Reducing the number of monocytes is a fairly infrequent condition; the determining causes can be acute infections, acute leukemias and reduced bone marrow function (marrow aplasias, myelotoxic drugs, etc.).

A low number of monocytes in the blood ( monocytopenia ) can also occur due to the release of toxins in the blood from some bacteria (endotoxin), as well as in those who carry out chemotherapy.

How to measure them

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

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 monocytes or macrophages, 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

• There are many diseases that can lead to an increase or decrease in the values ​​of monocytes. For this reason, in the event that blood tests return abnormal values ​​of monocytes in the blood, it is advisable to contact your doctor immediately; he is able to identify the possible cause of the alteration and establish the most correct therapeutic path.
• The increase in the number of monocytes in the blood ( MONOCYTOSIS ) generally indicates the presence of an ongoing infectious disease.

  The presence of monocytes to a greater extent than the norm occurs also in autoimmune diseases, in hematological diseases and in some types of tumors. Macrophage proliferation in tissues occurs in response to infections, sarcoidosis and Langerhans cell histiocytosis.

• A low number of monocytes in the blood ( MONOCYTOPENY ) can be found during acute infections, acute leukemias and reduced bone marrow function (bone marrow aplasia, chemotherapy, etc.).