Types and function of white blood cells (leukocytes)

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White blood cells (white blood cells) are part of the immune system. They help fight infection and protect the body from other foreign materials.

Different types of white blood cells have different functions. Some are involved in identifying intruders. Some kill harmful bacteria. Others make antibodies to protect your body from bacteria and viruses.

This article looks at the different types of white blood cells and their different functions.

Types of white blood cells

Leukocytes are also known as leukocytes . They are the body's defenses against infection. There are several different types for different purposes.

Some of the cells are part of our innate immune system, which means that they can attack foreigners from birth. Others are part of our humoral or learned immune systems. Humoral immune cells produce antibodies when they come into contact with a microbe. Therefore, the body can be prepared for a new attack from this microbe.

Get Medical Information / Ellen Lindner

Neutrophils

Neutrophils make up about half of the white blood cell population. They are usually the first cells of the immune system to respond to invaders such as bacteria or viruses.

As first responders, they also send signals that warn other cells of the immune system to arrive.

Neutrophils are the main pus cells. Once released from the bone marrow, these cells live for only about eight hours. Your body makes about 100 billion of these cells every day.

Eosinophils

Eosinophils also play a role in fighting bacteria. They are also very important in fighting parasitic infections (such as worms).

They are perhaps best known for their role in the appearance of allergy symptoms. Eosinophils can overdo it by creating an immune response against something harmless. For example, eosinophils mistake pollen for alien invaders.

Eosinophils make up no more than 5% of the white blood cells in your bloodstream. However, there are high concentrations of eosinophils in the digestive tract.

Basophils

Basophils make up only about 1% of leukocytes. These cells are perhaps best known for their role in asthma. However, they are important for the formation of a nonspecific immune response to pathogens, organisms that can cause disease.

When stimulated, these cells release histamine, among other chemicals. This can cause inflammation and narrowing of the airways.

Lymphocytes (B and T)

Lymphocytes are also important for the immune system. They are of two types: B cells and T cells. Unlike other white blood cells, which provide non-specific immunity, B and T cells have specific targets.

B lymphocytes (B cells) are responsible for humoral immunity, which is an immune response in which antibodies participate. B cells produce antibodies that "remember" the infection. They are ready in case your body is exposed to this pathogen again.

T cells recognize certain foreign invaders and are responsible for their direct destruction. The 'memory' T cells also remember the invader after infection and react quickly if seen again.

B lymphocytes play a key role in the effectiveness of many modern vaccines. In some cases, such as the tuberculosis and whooping cough vaccines, T cells are the main players.

Monocytes

Monocytes are the garbage trucks of the immune system. About 5% to 12% of the white blood cells in the bloodstream are monocytes. Its most important function is to clean dead cells from the body.

Summary

White blood cells, more commonly known as white blood cells, take different forms that perform different functions in the immune system. This includes:

  • Neutrophils are the first response of immune cells.
  • Basophils release histamine to induce a nonspecific immune response.
  • Eosinophils fight bacteria and parasites, but they also cause allergy symptoms.
  • Lymphocytes are B and T cells that defend themselves against certain invaders.
  • Monocytes clean dead cells.

How leukocytes are formed

White blood cells are formed in the bone marrow through a process called hematopoiesis. All blood cells are derived from common hematopoietic stem cells (HSCs). It is also called a "pluripotent" stem cell. These stem cells differentiate, or specialize, at different stages.

HSC first divides into a lymphoid or myeloid stem cell.

The lymphoid stem cell gives rise to a lymphoid cell line. It is a family of cells that produce B cells and T cells.

Myeloid stem cells give rise to cells called myeloblasts. They later become macrophages, monocytes, neutrophils, basophils, and eosinophils. Myeloblasts can also turn into red blood cells and platelets.

Laboratory values

A normal white blood cell count is usually 4,000 to 10,000 cells per microliter (μL) .

Increased white blood cell count.

Infections usually cause an increase in the white blood cell count, but there are other possible causes. The number of leukocytes can increase due to overproduction. In other words, the body can release white blood cells from the bone marrow early.

Stress in any form can cause the release of white blood cells. Some causes of high white blood cell count include:

In severe infections, immature white blood cells called blasts may be present. Blasts often occur when the body tries to quickly get white blood cells to the scene.

Low white blood cell count

Conditions that can cause a decrease in the white blood cell count include:

  • Severe infections
  • Bone marrow damage or abnormalities, such as aplastic anemia , bone marrow "seizure" from blood cancer or metastatic cancer, or damage from drugs or chemicals in the bone marrow
  • Autoimmune diseases like lupus.
  • Spleen sequestration, when leukocytes accumulate in the spleen.

Symptoms

On its own, a low white blood cell count has no symptoms. But low cell counts often lead to infection because there are not enough white blood cells to fight the invader. Symptoms of an infection can include:

  • Hot
  • Cough
  • Frequent or painful urination
  • Blood in the stool
  • Diarrhea
  • Redness, swelling, or warmth in the area of infection.

Chemotherapy

One of the most common and dangerous side effects of chemotherapy is its effect on white blood cells, known as neutrophils. As a reminder, neutrophils are the first responders of our immune system.

A decrease in neutrophils during chemotherapy, known as chemotherapy-induced neutropenia , increases the risk of serious infections.

Neutropenia makes it difficult to fight infection. As a result, bacteria, which are generally not very harmful, can cause serious illness.

Summary

White blood cells are an important part of our immune system. Different types of white blood cells have different functions in the body. In general, white blood cells help protect us from bacteria, viruses, and parasites.

A high white blood cell count is usually a sign of infection or disease. A low white blood cell count may indicate another type of problem. A low white blood cell count can leave you vulnerable to serious infections. Chemotherapy is a common cause of low white blood cell counts.

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