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White Blood Cells

Say you’ve just gotten sick. How does your body fight back and work to make you better again? A major part of your immune system that does this is your white blood cells (WBCs) or leukocytes. White blood cells don’t comprise a large amount of blood. However, they play a large role in finding and getting rid of viruses and germs.A D illustration of white blood cells moving with red blood cells through a blood vessel.

What are White Blood Cells?

WBCs are a part of your blood that is in charge of finding and attacking things that make you sick. They make up about 1% of your blood. Unlike red blood cells, WBCs don’t have hemoglobin, which allows RBCs to carry oxygen. Also unlike red blood cells, WBCs have nuclei. WBCs are typically made in either the bone marrow like red blood cells or sometimes in lymph nodes. 

An illustration of the bodies lymphatic system.

This is your lymphatic system.

Types of WBCs and Their Functions

  • Neutrophils are the most common type of WBC. They make up anywhere from 55-70% of all WBCs. They live for usually less than a day, so your body must continually produce them. They act as the first line of defense when something foreign comes to invade your body. 
  • Eosinophils typically protect your body against parasitic infections.
  • Basophils release a chemical called histamine when your allergies act up. Histamine causes symptoms like swelling, runny noses, or itchy eyes. 
  • Monocytes become macrophages when germs enter your body. Macrophages eat those germs and dead cells in your body. 
  • Lymphocytes separate into two groups: T lymphocytes and B lymphocytes. T lymphocytes mature in the thymus gland (T for thymus). They regulate the activities of other immune cells or directly attack germs. B lymphocytes produce antibodies, which specifically target foreign bacteria. They grow up in bone marrow, which is where the B comes from!

What Happens If You Have Too Many WBCs?

Having too high a white blood cell count could indicate that you’re under a lot of physical or emotional stress. Certain types of cancer also result in a high WBC count. For example, leukemia is a type of cancer in which too many white blood cells are dividing, but they’re not functional. Thus, they take up a lot of space, crowding out healthy WBCs that actually do work.  

Other Great Resources

What Are White Blood Cells? (University of Rochester Medical Center Health Encyclopedia): https://www.urmc.rochester.edu/encyclopedia/content.aspx?ContentTypeID=160&ContentID=35

Immune System, part 1 (CrashCourse): https://www.youtube.com/watch?v=GIJK3dwCWCw&t=197s

Effects of a Low WBC Count: https://www.childrensoncologygroup.org/index.php/lowwhitebloodcellcount


Written by: Sylvia Choo