What Does It Mean If Your Monocyte Levels Are High

What Does It Mean If Your Monocytes Are High?

Monocytes are white blood cells that help fight infections and other diseases. They are found in all parts of the body but their main function is to fight infection. They have two types: macrophages and activated lymphocytes. Macrophages are the type that normally attack bacteria, viruses and other microorganisms. Activated lymphocytes are those that normally fight cancerous cells such as leukemia or lymphoma. The normal range of monocytes is between 1,800 and 2,400 per microliter of blood. A normal range of activated lymphocytes is between 4,000 and 6,000 per microliter of blood.

A monocyte can differentiate into either a macrophage or an activated lymphocyte. This happens when a monocyte meets the correct antigen.

For example, a macrophage produces large amounts of antimicrobial peptides such as defensins. These peptides kill or disable pathogenic bacteria, viruses and other microorganisms. A activated lymphocyte produces a large amount of interleukin-12. This is a type of interferon that participates in the body’s immune response. Dendritic cells present antigen to the activated lymphocytes. The activated lymphocyte differentiates into a type that can respond to that antigen.

Monocytes normally live for about four to five days inside the body. They can also live for about one to two days outside the body.

This is long enough to travel through a cut in the skin and get into the body’s blood stream. The monocytes will then enter the bone marrow and begin to differentiate into either a macrophage or activated lymphocyte.

High Levels of Monocytes

High levels of monocytes can be caused by several factors. Some of these factors include:

-high temperatures


-cancer treatments that damage the bone marrow

-certain autoimmune diseases


High temperatures can lead to a condition called heat stroke. It can also damage the bone marrow and lead to a condition called Fanconi’s Anemia.

In this disease the patient produces fewer than 20 blood cells and platelets per minute. This prevents the patient from making antibodies or other blood cells that help fight infection. A low red blood cell count can also lead to increased exposure to monocytes. In this case, the body produces more red blood cells in an attempt to compensate. This can be fatal if the monocyte count is too high.

Infection can lead to an overgrowth of certain types of bacteria or another type of infection. It can also lead to autoimmune diseases like Rheumatoid Arthritis.

The body’s immune system begins to attack the body’s own connective tissue causing pain and damage to joints.

Cancer treatments that damage the bone marrow can lead to an increase in monocytes. This is especially true if the patient experiences a severe reaction to drugs used during treatment.

Certain autoimmune diseases are associated with a high monocyte count. This is due to the immune system attacking normal tissue.

In these diseases, monocytes play a secondary role. An example of this is lupus. The patient’s immune system attacks the body’s connective tissue particularly the heart and joints. Monocytes play a minor part in this process. They are secondary to other types of immune cells that cause inflammation.

Leukemia is a cancer of the white blood cells. This causes a monocyte overgrowth.

It can also cause other diseases of the blood. If the patient has a high monocyte count, the body will produce large amounts of other types of white blood cells. This is also called a mixed cell count or mixed cell leukemia. It’s important to note that leukemia is not caused by monocytes. In fact, leukemia is a very rare cause of high monocyte count. Broad-spectrum antibiotics will kill both normal white blood cells along with harmful monocytes.

High levels of monocytes can also occur with another type of cancer called Lymphoma. Lymphoma is a cancer that originates in the lymphatic system.

Cells from other parts of the body can enter the blood and affect the monocyte population. This is rare and in some cases the patient has elevated levels of monocytes due to another disease and cancer treatment. It is not spread through the blood. It does, however, leads to an increase in monocytes. This is because some types of cancer cells release substances that cause the body’s monocyte to grow and differentiate.

Sources & references used in this article:

Adiposity elevates plasma MCP-1 levels leading to the increased CD11b-positive monocytes in mice by K Takahashi, S Mizuarai, H Araki, S Mashiko… – Journal of Biological …, 2003 – ASBMB

Increased monocyte turnover from bone marrow correlates with severity of SIV encephalitis and CD163 levels in plasma by TH Burdo, C Soulas, K Orzechowski, J Button… – PLoS …, 2010 – journals.plos.org

Overexpression of monocyte chemoattractant protein 1 in the brain exacerbates ischemic brain injury and is associated with recruitment of inflammatory cells by Y Chen, JM Hallenbeck, C Ruetzler… – Journal of Cerebral …, 2003 – journals.sagepub.com

Quantification of CD4, CCR5, and CXCR4 levels on lymphocyte subsets, dendritic cells, and differentially conditioned monocyte-derived macrophages by B Lee, M Sharron, LJ Montaner… – Proceedings of the …, 1999 – National Acad Sciences

Increased ratio of circulating neutrophils to monocytes in amyotrophic lateral sclerosis by BJ Murdock, DE Bender, SR Kashlan… – Neurology …, 2016 – AAN Enterprises