What Are Monocytes? - Definition, Function & Blood Test

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  • 0:02 What Are Monocytes?
  • 0:50 Functions of Monocytes
  • 2:05 Monocytes in Blood Tests
  • 3:01 Lesson Summary
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Lesson Transcript
Instructor: Lynee Carter
In this lesson, you will learn about the white blood cells called monocytes, how they function in the immune system to fight germs and the causes of abnormal blood tests.

What are Monocytes?

We are surrounded by germs in our environment that can have a negative effect on us. They can cause us to be ill and give us harmful infections. In severe cases, they can cost us our lives. When these germs enter our bodies, our immune system views them as intruders that must be fought off. Our immune system has a key component called the white blood cells, of which there are several different kinds.

Monocytes are a type of white blood cell that fights off bacteria, viruses and fungi. Monocytes are the biggest type of white blood cell in the immune system. Originally formed in the bone marrow, they are released into our blood and tissues. When certain germs enter the body, they quickly rush to the site for attack.

Functions of Monocytes

Monocytes have several functions to help you ward off diseases and infections. To help you remember what they do, note that each function begins with the letter 'M.'

Monocytes Munch

Monocytes have the ability to change into another cell form called macrophages before facing the germs. They can actually consume, or munch, on harmful bacteria, fungi and viruses. Then, enzymes in the monocyte's body kill and break down the germs into pieces.

Monocytes Mount

Monocytes help other white blood cells identify the type of germs that have invaded the body. After consuming the germs, the monocytes take parts of those germs, called antigens, and mount them outside their body like flags. Other white blood cells see the antigens and make antibodies designed to kill those specific types of germs.

Monocytes Mend

Monocytes help mend damaged tissue by stopping the inflammation process. They remove dead cells from the sites of infection, which repairs wounds. They have also shown to influence the formation of some organs, like the heart and brain, by helping the components that hold tissues together.

Monocytes in Blood Tests

Doctors can tell a lot about what is going on with a person by whether they have elevated or lowered levels of monocytes in the blood. Elevated levels of monocytes are seen when people have infections, inflammatory diseases or certain types of cancers. This reflects the body's need for a large number of monocytes to help fight off the germs. Low levels of monocytes usually indicate having a condition that is suppressing the immune system response or from the body's inability to produce enough monocytes to stop an overwhelming amount of germs.

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