What are leukocytes and what are the normal values?

Leukocytes are the most important defense cells in the human body. Its concentration in blood is a reflection of the state of the immune system.

Last update: 06 July, 2022

The immune system is a complex network of cells and chemicals responsible for protecting the human body from germs and foreign bodies. Leukocytes are the most abundant immune cells in the body. Are you interested in knowing what are they and what are the normal values ​​of leukocytes? Next, we tell you.

Leukocytes, or white blood cells, are a group of blood cells that actively participate in the innate and adaptive immune response of each person, according to different studies. These are responsible for fighting infections and harmful substances, as well as eliminating abnormal cells of their own.

White blood cell levels in the blood are determined through a complete blood count or hematology. The percentage of leukocytes can increase or decrease in response to a wide range of diseases, so its determination is essential for the early diagnosis and treatment of many conditions.

Characteristics and functions of leukocytes

Leukocytes make up about 1% of an adult’s blood.

White blood cells are produced in the bone marrow from hematopoietic stem cells. In general, leukocytes are found in the blood, lymphatic vessels and in all tissues of the human body. In this way, the same represent up to 1% of the blood volume of an adult.

The so-called “white series” is able to move freely through the body and lacks pigment, unlike erythrocytes. Some of the functions of leukocytes include the following:

  • Recognize and differentiate harmful compounds.
  • Fight infections by bacteria, viruses, parasites and fungi.
  • Mediate inflammatory responses.
  • Modulate allergic reactions.
  • Eliminate abnormal cells, such as cancer cells.


Types of leukocytes

There are several types of leukocytes in the human body. These can be classified according to the shape of their nuclei and the presence or absence of granules in their cytoplasm. The type of leukocyte determines its specific functions within the immune system.

Those that have granules and several nuclei are called granulocytes and include the neutrophils, eosinophils Y basophils. On the other hand, those that do not have granules and have a single nucleus are called agranulocytes and include the lymphocytes Y monocytes.

  • neutrophils: They constitute 50 to 70% of total leukocytes and form the first line of defense against bacteria and fungi, according to studies.
  • eosinophils: actively participate against parasite infections and allergic reactions. They correspond to 2 to 3% of the white series.
  • Basophils: release histamine and other substances that modulate the inflammatory response. They are the least abundant leukocytes, constituting between 0.4 and 1% of white blood cells.
  • monocytes: travel in blood to all tissues and differentiate into macrophages. They have a very short life and form 5 to 6% of leukocytes.
  • lymphocytes: These white blood cells are common in the blood and in the lymphatic organs. They make up about 30% of the white blood cell and are responsible for recognizing harmful agents, releasing antibodies, and destroying damaged cells.

How are white blood cells measured?

The determination of the levels of leukocytes in the blood is called the white blood cell count.. This procedure makes it possible to identify the number of leukocytes from a venous blood sample. In addition, this test is part of the blood count, one of the most common routine tests.

Similarly, from this examination the concentrations of neutrophils, eosinophils, basophils, monocytes and lymphocytes are also recognized. These results are useful to assess the state of the immune system. and identify underlying diseases, such as bacterial and viral infections.

Normal values

The white blood cell count can vary depending on the age, the health status of the person and the standardization of each laboratory. Studies affirm that the normal values ​​of white blood cells in adults are between 4,500 and 11,000 leukocytes per cubic millimeter of blood (mm³). In childhood, it is possible to find the following normal ranges for leukocytes:

  • Newborns: 10,000 – 30,000 white blood cells per mm³.
  • Under 1 year old: 6,000 – 18,000 white blood cells per mm³.
  • From 2 to 5 years: 6,000 – 15,000 white blood cells per mm³.
  • From 6 to 12 years: 5,000 – 13,000 white blood cells per mm³.


high leukocytes

An increase in white blood cells may signal the presence of an underlying disease.

The increase in blood leukocytes above 11,000 white blood cells per mm³ It is called leukocytosis. This condition is usually accompanied by an elevation of neutrophils or lymphocytes, called neutrophilia and lymphocytosis, respectively.

Leukocytosis is a sign of underlying disease and often manifests with symptoms such as fever, swelling, shortness of breath, loss of appetite, dizziness, and chills. Some of the more common causes of increased white blood cells include the following:

  • Bacterial infections, such as pneumonia and meningitis.
  • Inflammatory processes, such as appendicitis, cholecystitis and diverticulitis.
  • Deep and extensive burns.
  • Severe bleeding.
  • Trauma.
  • Stress.
  • Cancer, such as leukemia.
  • Inflammatory bowel disease (IBD).
  • Intense parasites.
  • allergic crises.
  • Medications, such as cortisone, adrenaline, and heparin.

low leukocytes

The Spanish Society of Internal Medicine (SEMI) defines leukopenia as the decrease in white blood cells below 4,000 white blood cells per mm³. People with a low white blood cell count may experience excessive fatigue, frequent infections, headaches, and abdominal cramps. Among the most common causes are the following:

  • Autoimmune diseases, such as lupus.
  • Alterations of the bone marrow due to tumors or intoxication.
  • Effect of chemotherapy and radiotherapy.
  • Use of antibiotics, anticonvulsants and corticosteroids.
  • Liver or kidney disease.

How to maintain normal leukocytes?

In most cases, white blood cell levels return to normal by fixing the underlying cause. In this sense, it is important to follow the doctor’s instructions in detail. Similarly, it is possible to increase the number of white blood cells by including some foods in our diet. Such is the case of the following foods:

  • black tea
  • Yogurt.
  • Mushrooms, red pepper and spinach.
  • Oysters and shellfish.
  • Red meat and liver.
  • Almonds, peanuts and sunflower seeds.

The most important immune cells in the human body

As you can see, leukocytes are the main source of defense of the human body against invading germs and foreign substances. In most cases, changes in white blood cell levels are a clear sign that something is wrong with the body. For this reason, it is advisable to annually evaluate the state of the immune system through blood tests.

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