There are five different types of white blood cells found throughout our blood. Each with an important job, they fight off infection and work to keep us healthy. Learn more about these cells and take a quiz at the end.

What are White Blood Cells?

Our bodies are constantly under siege. If we could see into the world of tiny microorganisms, we would observe the constant attack of viruses and bacteria upon us. These potentially harmful intruders enter through any nook or cranny, be it our mouth and nose or an open cut. Sometimes we succumb to infection. However, fortunately for us, we are protected by an equally tough microscopic army within our own body.

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A Lymphocyte, One Type of White Blood Cell
lymphocyte

Welcome to the world of white blood cells. These tiny organisms serve as the armed forces of our body, fighting off intruders, patrolling for invaders, and even cleaning up. Also known as leukocytes, white blood cells represent our immune system. If not for these fighters, we may have succumbed to tiny potential killers long ago. There are five different types of white blood cells, each performing specific jobs to keep us healthy and alive. In this lesson, learn more about these cells and how they work for our body.

Where do White Blood Cells Come From?

Although there are several different types of white blood cells, they all come from the same place. White blood cells originate from stem cells in our bone marrow. The bone marrow is essentially a blood cell producing factory, pumping out billions of new cells every day. These freshly made white blood cells have the ability to move on their own. Once produced, they leave the marrow and enter the bloodstream.

However, it may surprise you to know that most white blood cells do not actually reside in the bloodstream. The majority of leukocytes are found outside the blood, in tissues and interstitial fluid. The ones that are found within the blood are typically just utilizing the bloodstream as a vehicle to get to another location. Like soldiers in charge of certain posts, white blood cells have specific areas and tissues in the body for which they are responsible.

The Five Types of White Blood Cells

Let’s take a look at the first type of white blood cell, the basophil. This is the least numerous of all the white blood cells. But it plays an important part in the inflammatory response of the body. For example, have you ever found yourself in a sneezing fit after walking through a field of flowers? This allergic reaction is due to the inflammatory response of the body as it attempts to get rid of the pesky pollen in your nose. A substance called histamine is released, causing your allergic reaction. Basophils produce and store the histamine that is used at a time like this.

The Five Types of White Blood Cells
Five Types of White Blood Cells

Next we have the eosinophil. This is also a rare white blood cell, but it has the ability to poison other microorganisms with deadly chemicals. The eosinophil is also on parasite patrol. It detects the presence of unwanted microorganisms and then unleashes its toxic proteins, killing the victim.

The neutrophil is the most numerous of all the white blood cells. In fact, the bone marrow produces 100 billion of these cells alone on a daily basis. About half of all the neutrophils are found in the bloodstream, and half are found in tissues. These cells are the immune system’s First Responders. For example, if a bacteria is detected, an alarm in the form of a chemical signal is sounded. Neutrophils race to the site and get to work. Using a process called phagocytosis, they engulf the bacteria and digest the unlucky victims.

Lymphocytes are a crucial and dramatic part of our immune system. These white blood cells give rise to antibodies and also brutally attack invaders. Specifically, there are two major types of lymphocytes: B-cells and T-cells. Each type of B-cell is programmed to make a specific antibody. If it comes into contact with that particular antigen, or invader, it commands an army of antibodies to be produced in epic numbers. This army will be ready for attack should that particular antigen ever be detected again. This immune response is the reason we don’t get the same exact virus twice.

T-cells have several different talents. Some tell nearby B-cells to produce antibodies. And some, called killer T-cells, have the ability to directly attack cells that are recognized as bad, such as cancer cells. Like bounty hunters, killer T-cells locate and launch an attack on these abnormal cells. Another type, called natural killer cells, work in a similar manner but kill by way of chemical warfare. They release toxic chemicals onto their prey, killing them instantly.

T-cell
T-cell

Finally, monocytes are the largest of the white blood cells. After leaving the bloodstream and heading into various tissues, these cells eventually mature into cells called macrophages. Macrophages are a major part of the cleanup crew of the immune system. One can only imagine the mess left behind as war is constantly waged against invaders in the body. By the process of phagocytosis, these giants engulf and ingest debris and dead cells. Macrophages also have the capability of swallowing up other foreign objects such as living bacteria and parasites.

Macrophage Engulfing a Particle
macrophage

Lesson Summary

White blood cells make up our immune system. There are five different types of white blood cells, most of which are not found within the bloodstream. Basophils store histamine, released during the inflammatory response. Eosinophils poison their prey and target parasites. Neutrophils are alerted to the sites of injury or intruders, and by phagocytosis they engulf and digest their victims. Lymphocytes include B-cells and T-cells, from which antibodies arise. Finally, monocytes eventually become large cells known as macrophages, which engulf large particles and help clean up.