Functions of monocytes
Monocytes are leukocyte elements involved in the body's immune defense. These white cells perform the following functions:
- immature monocytes are the most “capable” cells of phagocytosis; they capture and inactivate foreign agents in the blood, be they pathogens or protein fractions of toxic origin;
- remove dead leukocytes from the source of inflammation;
- activate the synthesis of interferons;
- participate in thrombus formation;
- have an antitumor effect.
Monocytes are a serious barrier to infection. If eosinophils, lymphocytes and neutrophils die almost immediately when encountering pathogenic agents, then monocytes “enter the battle” repeatedly. This is the particular importance of monocytic indicators in the blood.
Main functions of monocytes
Monocytes are the largest white blood cells and play an important role in the body's fight against infections and parasites, and are also able to resist cancer cells, preventing them from spreading. Therefore, in cases where a person is sick, monocytes are usually elevated.
Monocytes are involved in the creation of substances that affect the level of blood clotting and the dissolution of a blood clot. They are formed in the bone marrow, and, leaving it along with other cells, circulate throughout the body in the blood for 2-3 days, on average up to 70 hours. After this, the cells leave the blood and are absorbed into nearby tissues, transforming into macrophages.
Monocytes are able to destroy bacteria and dead tissue, which promotes regeneration and overall healing. Monocytes are also involved in the process of blood formation and the synthesis of interferon, which helps to increase the body's immune defense against the invading virus, as they make healthy cells of the body immune to viral infection.
Thus, monocytes contribute to:
Protect the body from viruses and infections; Tissue restoration by creating favorable conditions for rapid regeneration; Protection against tumor formations; Removal of dead and damaged tissue; The synthesis of cytokines are small molecules whose main task is to transfer information from cell A to cell B in order to trigger a certain reaction in cell B.
The function of monocytes and leukocytes is to capture and absorb foreign cells, viruses and bacteria. This process has 2 phases:
- Foreign bodies attach to the monocyte cell.
- Absorption itself occurs, in other words, “digestion” and safe removal from the body.
The same functions are performed by monocytes that are already found in tissues; they are called macrophages. At the first stage, the process is accompanied by excitation of protoplasm, which leads to an increase in the need for oxygen. Proteins that have captured foreign cells are called activated, and the rate of their absorption by cells increases proportionally.
The second phase is characterized by an increase in monocytes and some of their enzymes, in the presence of which the need for additional energy necessary for the transport and absorption of foreign cells sharply increases. This phase is called protoplasmic, because metabolism increases during it. It is also characterized by a longer period compared to the first phase. It is also worth noting that viral cells and bacteria captured by monocytes cannot always be destroyed. Such foreign cells are called virulent and, being captured by monocytes, they are able not only to stay alive, but also to multiply, spreading the infection throughout the body.
Monocytes: norm and deviations
The norm of monocytes in the leukocyte formula of blood is 1 – 8% in percentage and up to 0.8 × 109/l in quantitative/absolute (abs) indicator. If the content of monocytes does not reach the norm, this indicates a failure of the immune system and the body’s defenselessness against infection and inflammatory diseases. Monocytopenia is observed with B12 deficiency and aplastic anemia, severe bone marrow damage, long-term severe purulent infections, general exhaustion and stress.
An increase in the percentage level of monocytes of more than 9–10% in an adult almost always characterizes pathology. There is a concept of relative monocytosis, when the quantitative indicator remains within the normal range, but its percentage increases. This deviation is observed when the number of neutrophils or lymphocytes decreases and does not carry a serious diagnostic load. Absolute monocytosis deserves attention - an increase in both quantitative and percentage indicators of monocytes.
Normal indicators
Monocytes are determined in a blood test to obtain a clinical picture of a person’s health status.
It should be borne in mind that the content of monocyte cells does not change immediately after exposure to any pathological process: the cells wait for lymphocytes to recognize harmful elements and only then begin to act.
Thus, it is possible to obtain test results that deviate from the norm only after some time from the onset of the disease.
In order for the laboratory technician to count monocytes in the blood during a general blood test, the doctor will make a note in the referral about the need to calculate the leukocyte formula of the patient’s blood.
Blood for analysis is often taken from a finger, but if a vein is taken at the same time for other studies, then you can take a little from a test tube to determine the level of monocytes.
In this case, you should follow the standard rules (take tests on an empty stomach, do not smoke and do not subject your body to heavy physical activity several hours before the examination).
Following these recommendations will help determine changes in blood composition due to pathologies, and not due to the influence of physiological processes.
The normal number of cells varies slightly between children and adults. Thus, for children under the age of 13 years, the norm is considered to be a monocyte content of 2 to 12%, for adults - from 3 to 11% of the total number of leukocytes.
READ When monocytes are elevated - what does it mean?
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These numbers are a relative indicator of the content of monocyte cells in the blood compared to the total number of leukocyte cells.
The absolute indicator of monocyte content is also very important when diagnosing certain diseases.
In this case, the number of elements is determined based on the calculation per 1 liter of blood. The norm for men and women is the same.
An exception is women during the first trimester of pregnancy, since an increase in the percentage of monocytes in this case may indicate activation of the immune system to protect the fetus.
The decision on drug correction of the number of monocytic cells can be made exclusively by the doctor observing the course of pregnancy.
If the results of the analysis reveal a decrease or increase in monocytes, the doctor will ask you to undergo additional examination to exclude a number of diseases.
The cause of changes in the level of monocytes in the blood, in addition to pathological conditions, may be a stressful condition or increased physical activity.
Reasons for increased monocyte levels, when you should not be afraid of deviations
Harmless monocytosis (the indicator gradually normalizes on its own) is observed:
- during the recovery period after an infectious disease - influenza, acute respiratory infections;
- in the initial phase of childhood infections - whooping cough, measles, scarlet fever, chickenpox;
- after surgery - removal of appendicitis, gynecological operations, etc.
The death of other types of immune cells in these conditions causes a compensatory response in the bone marrow and the production of new cells. The indicators of eosinophils and neutrophils that died at the very beginning are normalized already on days 2–3, provided there are no complications, and the level of “long-living” monocytes increases accordingly. Monocytosis during the recovery period is a sign that the body has coped with the infection.
Serious causes of monocytosis
Persistent monocytosis, expressed to varying degrees, may be a sign of the following diseases:
- massive helminthic infestation;
- severe viral infections - mononucleosis, mumps;
- fungal infection - candidiasis;
- specific bacterial infections - syphilis, tuberculosis;
- rheumatic pathology of joints and heart;
- enterocolitis - infectious intestinal diseases;
- septic endocarditis;
- autoimmune pathology - lupus, rheumatoid arthritis, sarcoidosis;
- hemorrhagic diathesis - thrombocytopenic purpura;
- hematological oncology - lymphogranulomatosis, myeloid leukemia;
- malignant tumors of various localizations.
Monocyte level during pregnancy
The monocyte count undergoes some changes during pregnancy, but does not go beyond the normal range for adults. Percentage of monocytes:
- I trimester - average 3.9%
- II trimester - 4.0;
- III trimester - 4.5.
Monocytes of a pregnant woman have a distinctive feature - they produce cytokines to a greater extent - substances with anti-inflammatory effects. A slight increase in monocytes in the first months of pregnancy is an adaptive response of the complex immune system to the state of pregnancy. At the same time, monocytes are more focused on neutralizing bacterial microorganisms, and antiviral protection is reduced. That is why a pregnant woman should have her blood tested for viral agents, especially the Epstein-Barr virus (type 4 herpes infection).
What is the norm of monocytes in the blood?
Only immature formed elements can be found in the bloodstream. Their number varies depending on the influence of physiological factors and human biorhythms. For example, the jump in monocytes in the blood is affected by food intake, the menstrual cycle, and physical activity.
Under normal conditions, approximately 2-9% of monocytic cells should be present in the bloodstream of an adult. This is a percentage of the total volume of leukocyte forms. In children, the level of mononuclear phagocytes is higher – ranging from 5 to 11%. But by the age of six, the norm approaches adult levels.
In a healthy body, macrophages have pronounced bactericidal properties. As soon as a focus of inflammation develops, they migrate to it, but not immediately. First, neutrophils are sent to the site of the inflammatory process. And then mature monocytes, like “orderlies,” rush to clean the damaged area from foreign particles.
Diagnostic data for monocytosis
Monocytosis is not considered as an independent indicator. The level of monocytes in combination with the indicators of other leukocyte elements provides sufficient information about the causative agent of the disease, the stage of the disease, the degree of the body’s immune defense and the effectiveness of the treatment. The following combinations are quite informative:
- Monocytosis and lymphocytosis
Monocytes and other leukocyte cells and lymphocytes are increased in viral diseases, respiratory pathologies, and childhood infections. In this case, a decrease in neutrophils is often recorded.
- Monocytosis and basophilia
Basophils are the immune component of the rapid response. It is these cells that are the first to rush to the pathological focus. Monocytosis and basophilia can occur due to long-term use of hormonal drugs. The combined increase in monocytes, basophils, lymphocytes and macrophages provokes an increase in the inflammatory reaction and massive production of histamine.
- Montocytosis and eosinophilia
This combination of leukocyte formula indicators is the result of an allergic reaction. Also observed with parasitic infection with intestinal worms, chlamydial inflammation and mycoplasma attack. Typically, such diseases produce a symptom that is distant from the lesion - a prolonged dry cough with painful attacks against the background of the absence of clinical symptoms and pulmonary wheezing.
- Monocytosis and neutrophilia
This tandem indicates a bacterial infection. In this case, a significant decrease in the lymphocyte level in the blood is always observed. Typical clinical picture: high temperature, purulent discharge from the nose, wet cough, wheezing and whistling during auscultation of the lungs.
Monocytes in the blood: functionality
Monocyte bodies quickly respond to the inflammatory process and immediately move towards the site of infection or introduction of a foreign agent. Almost always they manage to destroy the enemy. But there are situations when enemy cells turn out to be more powerful than the macrophage, block phagocytosis or develop protective mechanisms.
Mature monocytic bodies perform several main functions:
- Enzymes bind the antigen and show it to T-lymphocytes so that they recognize it.
- They form mediators of the immune system. Proinflammatory cytokines move to the site of inflammation.
- They take part in the transport and absorption of iron, necessary for the production of blood forms in the bone marrow.
- Phagocytosis is performed, going through several stages (binding, immersion in the cytoplasm, formation of a phagosome, destruction).
Leukocyte cells are not always able to phagocytose pathogenic microorganisms. There are certain pathogens, for example, mycoplasmas, which bind to the membrane and take root in macrophages. But mycobacteria and toxoplasma act differently. They block the process of fusion of phagosome and lysosome, thereby preventing lysis. To fight such microbes, they require external help from leukocytes that produce lymphokines.
Actively mature monocytes deal with microscopic invaders and even huge cells. They live in tissues for weeks, months. But unlike lymphocytes in the blood, they do not have immunological memory. Interestingly, the leukocyte cells remain in the tattoos and lungs of smokers for years because they cannot get out of them.
Treatment
Monocytosis is not an independent disease, it is only a sign (dangerous and not so) of a pathological process in the body. The components of the leukocyte formula are able to replace each other to compensate for insufficient functions. In most cases (ARVI, helminthiases, etc.), the deviations are not clearly expressed and are eliminated on their own after full treatment of the identified disease for 1 - 2 weeks. Serious pathology, including cancer, is indicated by:
- sharp changes in leukocyte parameters, monocytes inclusive;
- long-term deviations.
In this case, additional laboratory and instrumental studies are carried out to determine the exact cause of the blood composition disorder. Therapeutic tactics are chosen in accordance with the identified disease, and a follow-up complete blood test helps monitor the healing process.
Causes of elevated monocyte levels
A high percentage of monocytes in the blood is called monocytosis. In most cases, it occurs with a common cold or runny nose. However, as you know, phagocytes are “cleaner” cells, and they work with many different diseases. Therefore, the number of reasons that provoked their growth is also quite large. Here are the main ones:
- Infections (fungal, herpes, etc.)
- Blood diseases such as leukemia and mononucleosis
- Autoimmune diseases: arthritis, arthrosis, etc.
- Rheumatism (inflammatory connective tissue disease)
- Endocarditis (inflammation of the inner lining of the heart)
- Inflammation of the gastrointestinal tract
- Tumor formations
Patients with monocytosis may feel tired, tired, and have a drop in temperature. In general, nothing definite, such symptoms occur in thousands of other ailments, therefore, in order to exclude all of the above diseases, it is advisable to conduct an additional examination of the body after receiving the results of a blood test. In this way, you can stop the development of an unwanted disease in the bud and protect yourself and your children. At the same time, you should not be scared and panic, and also do not decipher the test results yourself, even if you know the normal parameters, because everyone’s circumstances and state of health are individual - it is better to consult with your doctor, he will advise you what to do in the current situation. With this problem, it is best to contact a therapist or a hematologist - a specialist who deals with blood issues.
Inflammatory processes in the human body can also be indicated by test results such as ESR (erythrocyte sedimentation rate) and the level of eosinophils (another type of white blood cell) - these parameters should also be paid attention to, sometimes they are elevated in the presence of worms in the intestines or allergies.
