Monocytes are a type of white blood cell in your immune system. Monocytes turn into macrophage or dendritic cells when an invading germ or bacteria enters your body. The cells either kill the invader or alert other blood cells to help destroy it and prevent infection.
Monocytes are a type of white blood cell (leukocytes) that reside in your blood and tissues to find and destroy germs (viruses, bacteria, fungi and protozoa) and eliminate infected cells. Monocytes call on other white blood cells to help treat injury and prevent infection.
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Monocytes are your cell’s firefighters. Their lifecycle begins in the bone marrow (soft tissue inside of your bones) where they grow and train to protect your body. Once they mature, they enter your bloodstream and tissues to defend your body against foreign invaders, like germs.
Germs are similar to fires when they enter your body. Once germs are inside your tissues, monocytes hear an alarm, calling them into action to fight the fire. These cellular firefighters differentiate into two types of cells:
Dendritic cells are your fire department’s call center. They're responsible for alerting other cells in your body to help fight infection. Dendritic cells reside in superficial tissues, such as just beneath your skin and in the lining of your nose, lungs, stomach and intestine. When a germ enters the body’s tissues, dendritic cells collect the antigen of the invading germ (the molecule in the germ that produces an antibody response) and release proteins (cytokines) that notify other white blood cells to come to the site of the infection and destroy the invader.
Macrophages are on the front lines of the fire, fighting germs (viruses, bacteria, fungi and protozoa) that enter your body. Macrophage cells surround the invading germ and ingest and kill it with toxic enzymes within the cell. These cells also help remove dead cells from your tissues and bloodstream.
Monocytes are the largest type of white blood cell and are nearly twice the size of a red blood cell. Under a microscope, monocytes are easy to identify based on their size. Monocyte cells have a two-bodied nucleus (bilobed nuclei) center that floats in a contained fluid called cytoplasm.
A lab technician will add a stain to better view the cells under a microscope, which turns the components of the cell a pale to dark blue and purple color. Within the cytoplasm are tiny grain-like granules that may appear light purple. The nucleus changes shapes as the cell moves throughout your body. The monocyte’s nucleus appears dark purple in the center of the cell and can take the shape of:
Monocytes form in the soft tissue of your bones (bone marrow). After the cells mature, they travel to your tissues where they defend your body from infection alongside other cells in your immune system.
Conditions vary based on the number of monocytes in your blood. Your monocyte count can be too high or too low as a result of your body fighting an infection or disease.
Monocytosis occurs when your monocyte count is too high. It's most often linked to a chronic infection or disease that your body is fighting. Causes of monocytosis include:
Monocytopenia occurs when your monocyte count is too low. This is the result of decreases in your white blood cell count. Causes of monocytopenia include:
A normal monocyte count is between 2% and 8% of your white blood cell count. This equals about 200 to 800 monocytes per microliter of blood in healthy adults. If your monocyte count is outside those ranges, you're at risk of acquiring a monocyte-related condition.
A blood test checks the health of your monocytes. Two tests specifically identify how many monocyte cells are in your body:
If you have a low or high monocyte count, you most likely won’t experience any symptoms from the count itself. Instead, any symptoms you might feel are a side effect of a disorder that caused your monocyte count to be abnormal. Symptoms of monocyte disorders include:
Treatment is dependent on your diagnosis and the severity of your condition. It could be as simple as changing your diet or as significant as treating an underlying condition with chemotherapy. Your healthcare provider will offer treatment options specific to your diagnosis to help you decide on the best way to either increase or decrease your monocyte count.
Treatment to reduce your high monocyte count includes:
Treatment to increase your low monocyte count includes:
You can keep your monocyte cells healthy by:
A note from Cleveland Clinic
Monocytes are your body’s firefighters to stop germs from spreading fires (infections) in your tissues and blood. You can keep your monocytes healthy by taking steps to boost your immune system, which includes getting adequate sleep, eating a well-balanced diet and practicing good hygiene to prevent infection.
Last reviewed by a Cleveland Clinic medical professional on 11/28/2021.
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