White blood cells are vital components of the blood. Their role is to fight infection, and they are essential for health and well-being.
If a person has a high white blood cell count, it may indicate that they have an infection and that the immune system is working to destroy it. It may also be a sign that the person is experiencing physical or emotional stress. People with particular blood cancers may also have high white blood cells counts.
A low white blood cell count can signal that something is destroying the cells faster than they are being made, or that the body is producing too few of them.
White blood cells account for approximately 1 percent of the total blood cells, and they are essential to normal immune function. White blood cells are also known as leukocytes.
The white blood cells have a very important function in protecting the body from attack. This can be from bacteria, viruses, or other foreign substances that the body sees as some kind of threat.
White blood cells are continuously produced in the bone marrow and kept ready within the blood and lymphatic systems until they are needed.
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Number and type of white blood cells
White blood cells or leukocytes are components of the blood that protect the body against disease and foreign invaders.
Most people will produce large numbers of white blood cells, around 100 billion per day. Normal reported laboratory levels are between 4,000 and 11,000 cells per microliter of blood, although this can vary according to a person's race.
There are several different types of white blood cells, each with varying responsibilities:
- Lymphocytes are vital for producing antibodies that help the body to defend itself against bacteria, viruses, and other perceived threats
- Neutrophils are powerful white blood cells that destroy bacteria and fungi
- Basophils alert the body to infections by secreting chemicals into the bloodstream, mostly to combat allergies
- Eosinophils are responsible for destroying parasites and cancer cells, and they are part of an allergic response
- Monocytes are responsible for attacking and breaking down germs or bacteria that enter a person's body
When they are needed, monocytes travel to other organs, such as the spleen, liver, lungs, and bone marrow, where they transform into a cell called a macrophage. A macrophage is responsible for many cellular functions, including removing dead or damaged tissue, destroying cancer cells, and regulating the immune response.
High levels of white blood cells
An increase in white blood cells is known as leukocytosis. It typically occurs in response to the following conditions:
- Medications such as corticosteroids
- A bone marrow or immune disorder
- Certain cancers such as acute or chronic lymphocytic leukemia
- Inflammation such as that experienced with rheumatoid arthritis
- Emotional stress
- Allergic reactions
- Excessive exercising
In some cases, all white blood cells are affected. However, some people have a specific disease in which only one type of white blood cell is affected.
If levels of one particular type of white blood cell rise, this may be due to a specific trigger.
- Monocytes: If a person has high levels of monocytes, it may indicate the presence of chronic infection, an autoimmune or blood disorder, cancer, or other medical conditions.
- Lymphocytes: If there is an elevation in the level of lymphocytes, the condition is known as lymphocytic leukocytosis. This may occur as a result of a virus, or an infection such as tuberculosis. It may also be linked to specific lymphomas and leukemias.
- Neutrophils: If a person has heightened levels of neutrophils in their body, the disorder is known as neutrophilic leukocytosis. This condition is a normal physical response to an event, such as infection, injury, inflammation, some medications, and certain types of leukemia.
- Basophils: Increased levels of basophils may occur in people with a history of underactive thyroid disease, known as hypothyroidism, or in certain other medical conditions.
- Eosinophils: If a person registers high levels of eosinophils, the body may be reacting to a parasitic or other infection, allergen, or asthma.
Sometimes, there is no identifiable cause for the rise in white blood cells. This is known as idiopathic hypereosinophilic syndrome. It can lead to serious complications, such as heart, lung, liver, skin, and nervous system damage.
Those affected by idiopathic hypereosinophilic syndrome may experience symptoms such as:
- Weight loss
- Night sweats
- Chest pain
- Stomach ache
- Skin rash
Other imbalances of white blood cells
A blood test may be used to determine the white blood cell count.
If levels of white blood cells are lower than usual, this may be a sign that the person has a weakened immune system, due, for example, to HIV or AIDS. This deficiency is why people with these diseases are more susceptible to infection.
Abnormal blood cell production is also a feature of cancers, such as leukemia and lymphoma.
A number of conditions, collectively known as myeloproliferative disorders, can occur in the bone marrow. These develop when too many immature blood cells are produced, leading to an imbalance. These are rare conditions that may or may not be malignant.
Signs, symptoms, and complications
If the white blood cell count is too high this can indicate that there is a problem such as cancer or an infection. A blood test can be used to assess the white blood cell count, and other tests will be needed to pinpoint the exact cause of the problem.