What is a White Blood Cell?

Pouches of blood.
A diagram showing different types of white blood cells.
Blood, including white blood cells.
A neutrophil, the most common type of white blood cell.
Red blood cells, which exist alongside white blood cells.
A white blood cell.
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  • Written By: Michael Anissimov
  • Edited By: Bronwyn Harris
  • Last Modified Date: 04 October 2014
  • Copyright Protected:
    2003-2014
    Conjecture Corporation
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White blood cells are the body’s sentries, serving as the backbone of the immune system. White blood cells are found throughout the body, in both the blood and the lymphatic system. White blood cells have a density of about 4-11 billion per liter of blood. The scientific name for a white blood cell is leukocyte, simply meaning “white cell.”

White blood cells get their name from their color – white. This color was first discovered when blood was put into high-speed centrifuges and separated into its components. In healthy individuals, white blood cells make up about 1% of the blood. In sick individuals, this percentage increases substantially. The ratio of white blood cells in the blood can be used as a diagnostic of illness.

There are several different types of white blood cells, all with subtly varying functions. Some of the most common are neutrophils (65%), lymphocytes (25%), monocytes (6%), eosinophils (4%), and basophils (1%). White blood cells originate from stem cells in bone marrow. Scientists are working on ways to use stem cells to mass-produce white blood cells at will, which could be used for immune-boosting therapies.

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Neutrophils are the most common and the first line of defense against bacterial and fungal infections. Pus consists of large numbers of dead neutrophils. Neutrophils, like most white blood cells, engage in phagocytosis, that is, the consumption and digestion of bacteria or other foreign materials. Neutrophils can detect if a cell is part of the body or foreign by checking the molecules on its surface. Neutrophils function as suicide bombers – they cannot replenish the lysosomes used to digest microbes, so after killing a few bacteria or fungi, they simply die.

Lymphocytes are the second most common type of white blood cell. There are a variety of different lymphocytes. Their functions include the production of antibodies — protein tags that help the body identify invaders — immune system coordination, and destruction of body cells which have become contaminated with foreign material.

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anon350549
Post 7

Can you name the parts?

anon321465
Post 6

What is the scientific reason for abnormal white blood cells?

anon180204
Post 4

my wbc is only 3.6. am i in danger?

hyrax53
Post 3

@ameraus, either low or high white blood cell count could be caused by any number of conditions, including a nutrient deficiency or another illness that affects immunity. I would imagine she needs to get other tests to determine the cause.

widget2010
Post 2

If you want to think about things like white blood cells in a more fun light, there are stuffed toys called Giant Microbes that make great toys for anyone. I got some at thinkgeek.com, but I think you can buy them other places too. They have ones like the white blood cells, which are adorable, but also many different disease microbes. I have both the white blood cell and the mononucleosis, and they're so cute. They can be great for getting kids interested in science, especially biology.

ameraus
Post 1

My wife has just been told that her white blood count is slightly high and am wondering if her having MS could cause this?? Or what other reasons could cause this?

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