White blood cell facts for kids

Quick facts for kids White blood cell
A scanning electron microscope image of normal circulating human blood. In addition to the irregularly shaped leukocytes, both red blood cells and many small disc-shaped platelets are visible.
System	Immune system

White blood cells, also known as leukocytes, are special cells in your body. They are a key part of your immune system, which is like your body's defense team. Their main job is to protect you from germs that cause sickness and other things that don't belong in your body.

What are White Blood Cells?

Most white blood cells are neutrophils or lymphocytes.

Imagine your body as a magnificent castle, and white blood cells are its brave knights and guards! They are super important cells that are part of your immune system. Their main job is to protect your body from invaders like bacteria, viruses, fungi, and other foreign things that can make you sick. They are always on patrol, ready to spring into action.

Where Do They Come From?

All white blood cells start their journey in a special place inside your bones called the bone marrow. Think of the bone marrow as a busy factory that produces all sorts of blood cells, including these amazing immune cells. From there, they travel throughout your body, including your blood and a network called the lymphatic system, always looking for trouble.

What Makes Them Special?

One cool thing about white blood cells is that they all have a nucleus, which is like the control center of a cell. This makes them different from red blood cells, which don't have a nucleus once they're mature. Having a nucleus allows white blood cells to do many complex jobs, like making new proteins and responding to different threats.

How Many Are There?

Even though they are so important, white blood cells make up only a small part of your blood – about 1% of the total volume in a healthy adult. Red blood cells, which carry oxygen, are much more numerous, making up about 40% to 45% of your blood! But don't let that small percentage fool you; this 1% makes a huge difference to your health.

Doctors can measure the number of white blood cells in your blood with a simple test. A normal count is usually between 4,000 and 11,000 white blood cells in just one tiny drop (called a microliter) of blood. If these numbers go up or down, it can give doctors clues about what's happening inside your body.

Why Are They Called "White Blood Cells"?

The name "white blood cell" comes from how they look when scientists separate blood samples. If you spin a tube of blood very fast, it separates into layers. The red blood cells go to the bottom, the liquid part (plasma) stays on top, and in between, there's a thin, usually white layer. This layer is called the "buffy coat," and it's where the white blood cells are found! The scientific term "leukocyte" also means "white cell" in Greek (leuk- means "white" and cyt- means "cell").

Types of White Blood Cells: Your Immune Team

Your white blood cell team isn't just one type of cell; it's made up of several different kinds, each with its own special skills! You can remember the five main types with a fun phrase: "Never Let Monkeys Eat Bananas."

• Neutrophils
• Lymphocytes
• Monocytes
• Eosinophils
• Basophils

Let's meet the team!

Neutrophils: The First Responders

Neutrophils are the most common type of white blood cell, making up about 60–70% of the team. Think of them as the "first responders" or the police officers of your body. When bacteria or fungi try to invade, neutrophils are usually the first ones on the scene. They rush to the infection site, gobble up the invaders, and destroy them. When many neutrophils fight and die in a battle, they can form what we call "pus" in a wound – it's a sign they've been working hard! They have a unique nucleus that looks like it has many lobes, or sections, connected by thin strands.

Eosinophils: The Allergy and Parasite Fighters

Eosinophils make up a smaller part of your white blood cells, about 2–4%. These cells are especially good at dealing with parasitic infections, like certain worms that might try to live in your body. They also play a big role in allergic reactions, like when you have hay fever or asthma. When you have allergies, your eosinophil count might go up. Their nucleus usually has two lobes, connected by a thin strand.

Basophils: The Allergy Alerters

A basophil

Basophils are the rarest of the white blood cells, less than 0.5% of the total. They are like the alarm system for allergies! When your body encounters something it's allergic to, basophils release special chemicals, like histamine. Histamine helps widen blood vessels, which increases blood flow to an injured area, bringing more immune cells to help. They also release heparin, which helps prevent blood from clotting too quickly, allowing other cells to move around easily. Their nucleus is often hidden by many dark, coarse granules in their cytoplasm.

Lymphocytes: The Smart Defenders

Lymphocytes are more common in your lymphatic system than in your blood. They are the "strategists" and "memory keepers" of your immune system. There are a few important kinds of lymphocytes:

• B cells: These cells are like the "antibody factories." They make special proteins called antibodies that can stick to germs, marking them for destruction or stopping them from causing harm.
• T cells: These are like the "commanders" and "assassins." Helper T cells help coordinate the entire immune response, telling other cells what to do. Cytotoxic T cells (also called "killer T cells") are like highly trained assassins; they find and destroy cells in your body that have been infected by viruses or have become abnormal.
• Natural Killer cells: These cells are like the "silent guardians." They can recognize and kill cells that look suspicious, like cells that might be infected or have changed in a way that could be harmful.

Lymphocytes have a large, round nucleus that takes up most of the cell.

Monocytes: The Mighty Vacuum Cleaners

Monocytes, the largest type of white blood cell, are like the "super vacuum cleaners" of your body! They gobble up dead cell debris and attack microorganisms, just like neutrophils. But monocytes are even longer-lived and have an extra special job: they can present pieces of the invaders they've eaten to T cells. This helps the T cells "learn" about the invaders, so your body can remember them and fight them off even faster next time. When monocytes leave your bloodstream and settle in tissues, they become even bigger cells called "macrophages," which continue their cleaning and fighting duties. They have a distinctive kidney-shaped nucleus.

Fixed Leukocytes: Settling Down for Defense

Some white blood cells, like certain types of macrophages and dendritic cells, don't just stay in the blood. They migrate into different tissues and organs of your body and take up permanent residence there. They still play a vital role in the immune system, acting as local guards in places like your liver (where they are called Kupffer cells) or your brain (called microglia).

Checking Your White Blood Cells

A test called a differential count can tell doctors how many white blood cells you have in your blood. It also shows how many of each specific type of white blood cell is present. This helps doctors understand if your body is fighting something or if there's another issue.

White Blood Cell Problems

Sometimes, white blood cells don't work quite right. This can happen in a few ways:

• Too many white blood cells: This is called Leukocytosis. It's usually a good sign that your body is fighting an infection. But sometimes, it can mean there's an issue with how your cells are growing.
• Too few white blood cells: This is called leukopenia. It means your body might have trouble fighting off infections.

There are also times when the number of white blood cells is normal, but the cells themselves don't work as they should. Serious problems with white blood cells can include certain types of cancer, like leukemia and lymphoma.

Images for kids

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  Neutrophil engulfing anthrax bacteria

See also

In Spanish: Leucocito para niños