Monocytes are the biggest of all white blood cells that play an important role in the defense against germs and in inflammation. Read more below to learn about these cells and health effects of having higher or lower levels of monocytes.

Introduction

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Monocytes are the largest type of white blood cells (leukocytes). Approximately 2-10% of white blood cells are monocytes (R).

These immune cells circulate in the blood for several days before they enter the tissues where they become macrophages or dendritic cells (RR2).

Monocytes protect against viral, bacterial, fungal and protozoal infections (R).

These cells kill microorganisms, ingest foreign particles, remove dead cells, and boost immune responses (RR2R3).

However, they can also be involved in the development of several inflammatory diseases, including arthritis and atherosclerosis (R1, R2, R3). 

Monocyte Production in the Body

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In adults, blood cells are produced mainly in the bone marrow (R).

All blood cells originate from common parent cells called hematopoietic stem cells (R, R2).

The process of production of monocytes is called myelopoiesis (R).

Factors that control this process are:

  • Transcription factor PU.1 (R1R2R3R4)
  • Cytokines: SCF (Stem Cell Factor), GM-CSF (granulocyte-macrophage colony-stimulating factor), M-CSF (macrophage colony-stimulating factor, CSF1), IL-3, IL-6, and IFN-gamma (RR2R3R4)

After Monocytes Fulfill Their Job, What Happens Next?

Monocytes live for an average of 3 days before undergoing programmed cell death (R).

Monocytes live longer when there is inflammation. Once inflammation resolves, cell death occurs (R, R2).

Optimal Reference Range for Monocytes

Monocyte count should be between 0.20.8×109/L in adults (R)

Children have various normal ranges depending on age, ranging from 0.51.8×109/L in newborns, and gradually decreasing to 0.20.8×109/L in adolescents (R). 

High Levels of Monocytes (Monocytosis)

In monocytosis, the number of monocytes circulating in the blood is increased to more than 0.8×109/L in adults.

Conditions Associated with Monocytosis

Health Effects of Having A High Monocyte Count

1) Monocytosis Increases Risk of Atherosclerosis

Monocytes and macrophages are essential to the development and exacerbation of atherosclerosis (hardening of the arteries) that can lead to heart attack, stroke, and heart failure (R).

Monocytes accumulate in blood vessels, and contribute to the development and rupture of atherosclerotic plaque causing a blockage in blood vessels (RR2R3R4).

As hardening of the arteries progress, the number of monocytes in the blood rises (R).

2) Monocytosis May Increase Inflammation in Diabetes

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A clinical study that included 22 non-diabetic and 43 diabetic subjects showed no effect of diabetes on the number of circulating white blood cells, but monocytes were significantly increased (R). 

Monocytes may induce inflammation in diabetes.

Studies showed that monocytes secrete increased levels of TNF-alpha, IL-6, and IL-1 in both type 2 and type 1 diabetic patients (RR2R3R4R5R6).

3) Monocytosis is Associated with Increased Risk of Death in the Elderly 

Increased number of monocytes is associated with an increased risk of cardiovascular and cancer-related risk of dying in the elderly (R).

4) Monocytosis Facilitate Healing Process After A Heart Attack

After a heart attack, monocytes aid in removal of damaged and dead heart cells, and in healing heart attack damage to the heart (RR2).

Low Levels of Monocytes (Monocytopenia)

In monocytopenia, the number of monocytes circulating in the blood is decreased to less than 0.2×109/L in adults.

Conditions Associated with Monocytopenia

Health Effects of Having A Low Monocyte Count

1) Monocytopenia Lowers The Risk of Cardiovascular Disease

Out of all white blood cells, monocyte count has the strongest relationship with overall cardiovascular disease development in people with no symptoms.

Lower levels of monocytes are associated with a lower cardiovascular risk (R). 

2) Monocytopenia Increases Susceptibility to Infections

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Low monocyte counts increase susceptibility to infections.

Monocytopenia is associated with MonoMAC syndrome, which is characterized by increased susceptibility to mycobacterial, fungal, and human papillomavirus (HPV) infections (RR2).

3) Monocytopenia is Associated with a Risk of Hematologic Disorders

Monocytopenia is associated with a high risk of development of hematologic disorders (cancers of blood cells) such as myelodysplasia, acute myelogenous leukemia, chronic myelomonocytic leukemia, and lymphomas (R).

4) Monocytopenia Increases Risk of Cervical Cancer

Due to progressive monocytopenia, patients with primary immunodeficiency are susceptible to severe, persistant human papillomavirus (HPV) infections that can cause cervical cancer (R).

Ways to Increase Monocytes Levels

1) Acute Strenuous Exercise

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During the first few minutes of strenuous exercise, monocytes rapidly increase in the blood, but their numbers quickly decrease after the activity is done (R). 

2) Sauna

Sauna increases in white blood cells and monocytes, more so in athletes than in untrained subjects. This is because overheating the human body leads to elevated activity of monocytes (R). 

3) Cold Exposure

Prolonged cold exposure increases the number of monocytes which through the “fight or flight” (sympathetic) nervous system activation (R). 

4) Growth Hormone

Growth hormone injection increases white blood cell counts, which also increases monocyte counts (R).

5) Menopause

There is an increase in blood monocyte number during menopause. Moreover, monocyte counts decline following estrogen replacement therapy (R). 

6) Testosterone

Injections of testosterone into mice increased the number of monocytes, granulocytes and large lymphocytes in the blood (R).

7) Vitamin B12

Vitamin B12 helps increase white blood cell count, including monocytes in rats with protein deficiencies. However, supplementation with vitamin B12 does not change white blood cell count in rats that ate normal level of protein (R).  

8) Leptin

Human leptin increased monocyte growth and cytokine production, because leptin is a proinflammatory cytokine (R). 

9) Vitamin C

Recent studies suggest that vitamin C can modify immunity by inhibiting the programmed death of monocytes (R).

10) Calcitriol (Vitamin D3)

Calcitriol (vitamin D3) can increase growth of human monocytes (R).

11) Garlic

Garlic increases total white blood cell count. Rats fed with garlic have significantly more monocytes, neutrophils and lymphocytes than rats not fed with garlic (R). 

12) Chronic Alcohol Drinking

Alcohol consumption causes leaky gut, which allows lipopolysaccharides from Gram-negative bacteria in the gut to cause inflammation. Acute alcohol consumption initially mitigates the inflammation from LPS. However, chronic alcohol consumption can lead to a gradual increase of monocytes and inflammatory proteins, contributing to a general body state of inflammation (R). 

Prolonged alcohol intake also resulted in an increase in TNF-alpha production by monocytes (R)R2).

Ways to Decrease Monocytes Levels

1) Acute Alcohol Intake

Acute alcohol exposure influences immune functions, particularly monocyte function (R).

Studies suggest that acute alcohol consumption decreases inflammation in response to LPS in the gut (R).

Moderate alcohol consumption, 1 to 2 drinks per day, significantly reduced monocyte production of inflammatory cytokines, TNF-alpha and IL-1beta, and increased IL-10 production (RR2).

These mechanisms may contribute to the beneficial effects of moderate alcohol use on atherosclerosis.

2) Regular Exercise

Regular exercise is anti-inflammatory. Monocytes significantly decrease after a six-week course of moderate intensity cycling in overweight sedentary women.

Monocyte counts were also significantly associated with reduced triglyceride levels, increased insulin sensitivity, and decreased body mass index (R).

3) Weight Loss

In obese people, weight loss was accompanied by a significant reduction in monocyte and neutrophil counts. The decrease in circulating monocytes correlated with better insulin sensitivity (R). 

4) Omega-3 Fatty Acids

Regular consumption of omega-3 fatty acids, found in fish such as mackerel and salmon or fish oil supplements, may protect against atherosclerosis and heart disease (R).

People taking fish oil supplements were less likely to have inflammation in the blood vessel walls caused by monocytes. This effect was not as pronounced in people already taking medication to treat peripheral artery disease (R).

5) Mediterranean Diet

The Mediterranean diet may protect against inflammation caused by monocytes (R1, R2). The Mediterranean diet is comprised of foods such as seeds, nuts, vegetables, fruits and whole grains, and a lot of monounsaturated fats from olive oil.

6) Cortisol And Glucocorticoids

A single dose of cortisol decreases monocytes by 90% at 4 to 6 hours after treatment. This reduction persists for about 24 hours. Subsequently, monocyte levels return to normal 24 to 72 hours after treatment (R). 

This decrease is thought to be a consequence of redistribution of monocytes.

7) Estrogen And Progesterone

Estrogen, and possibly also progesterone, decrease monocyte count. This could explain decreased functioning of cell-mediated immunity during pregnancy (R).

8) Infliximab

Infliximab is an immune-suppressing drug for the treatment of several inflammatory diseases such as Crohn’s disease, ulcerative colitis, and rheumatoid arthritis (RR2R3).

Infliximab kill monocytes, which may help reduce inflammation in patients with chronic inflammatory diseases (R).

FDA Compliance

The information on this website has not been evaluated by the Food & Drug Administration or any other medical body. We do not aim to diagnose, treat, cure or prevent any illness or disease. Information is shared for educational purposes only. You must consult your doctor before acting on any content on this website, especially if you are pregnant, nursing, taking medication, or have a medical condition.

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