Basophils and their role in your body


Basophils are a type of white blood cell . Along with several other types, they play a role in your immune response as you fight an infection (most often caused by a parasite).

Basophils are also involved in some of the symptoms caused by allergic reactions, such as watery eyes, sneezing, and a runny nose.

Get Medical Information / Laura Porter


Basophils, like all blood cells, arise from stem cells in the bone marrow . They develop and differentiate through a process called hematopoiesis , during which blood cells change their structure and function. They are released from the bone marrow into the circulating blood as mature cells.

Blood cells that form in the bone marrow are divided into red blood cells, platelets, and leukocytes. For 700 erythrocytes (erythrocytes) there is approximately one leukocyte (leukocyte). Basophils constitute approximately 0.5% of the total number of leukocytes .

Basophils circulate in the blood and usually live for several days before degenerating and being replaced by new basophils.

White blood cells play a fundamental role in immune function and inflammation, red blood cells carry oxygen in their hemoglobin and oxygenate our body, and platelets help form blood clots, preventing blood loss.


Basophils are granulocytes, which means they contain small granules inside. The granules store and release enzymes and chemicals, particularly histamine , that contribute to the common inflammatory response found in basophils.

In a typical blood stain (a laboratory method used to evaluate cells), basophils appear bluish or purple, and many granules are often easily visible. Basophils are approximately 14-16 microns in diameter. To give an idea of their size compared to other cells, red blood cells are approximately 6.2 to 8.2 µm in diameter .


Basophils are part of the innate immune system, which means that they are activated when infectious organisms enter the body. They work in conjunction with other types of white blood cells, each with its own enzymes and chemicals to protect against invasion by microorganisms.

Congenital immune system

As part of the innate immune system, basophils do not make you immune to infections you have had in the past. They attack infectious organisms nonspecifically, even if you have never encountered this infectious organism before.

This means that the basophils do not remember the infectious organism, but simply recognize the invader as something that does not belong to their body and must be destroyed. Basophils are most effective at protecting against bacteria and parasites, including external parasites like ticks .

Action of basophils

The granules within the basophils contain histamine and heparin. Histamine is a vasodilator that causes blood vessels near the infection to dilate, allowing more immunomodulators to access the infectious body. Heparin is an anticoagulant substance made by the body that prevents blood clots from forming at the site of infection.

Basophils bind and can trigger the production of immunoglobulin E (IgE), an antibody that helps protect against parasites.

Basophils also participate in phagocytosis, which is the process of destroying an invading organism by disassembling it so that it cannot harm your body.

Diagnostic value

Basophils have diagnostic value because a high or low basophil count can indicate the type of disease. The value can be expressed as a percentage or as the actual number of cells per microliter (ml) of blood.

A complete blood count (CBC) is used to evaluate the composition of the blood. The normal percentage of basophils is 0.5% to 1% of the total white blood cell count (WBC) .

In contrast, the normal absolute number of basophils can range from 0 to 0.3 thousand per cubic millimeter (c / μl) . The absolute basophil count is calculated by multiplying the percentage of basophils by the total white blood cell count.

Blood test results can confirm whether you have abnormally high basophil levels (basophilia) or abnormally low levels (basopenia).

  • Basophilia can be a sign of chronic inflammation in which there is an overproduction of white blood cells. On the other hand, it could be due to an underactive thyroid gland ( hypothyroidism ) or a condition that causes an overproduction of white blood cells in the bone marrow .
  • Basopenia usually occurs with acute inflammation or infection, severe allergies, or an overactive thyroid gland ( hyperthyroidism ).

As a general rule, when evaluating the disease, the number of types of white blood cells is considered and not just one type. Basopenia or basopenia itself offers little more than a suggestion of where to start a diagnostic study.

Basophils and allergies

Basophils, along with IgE antibodies, can mediate reactions to allergens. Histamine secreted by basophils is one of the causes of common symptoms of seasonal allergies.

Histamine can cause watery eyes, itchy skin, and a runny nose. That is why antihistamines that block the action of histamine are effective in reducing allergy symptoms.

It is not entirely clear why these allergic reactions occur. In fact, an experimental study using basophils in people with allergies showed that basophils themselves were neither hyper-reactive nor hypo-reactive when extracted from the body, suggesting a more complex but not fully understood allergic mechanism .

Related conditions

The types of diseases associated with abnormal basophil values are very diverse and differ depending on whether the values are high or low.

Related to basophilia

Basophilia is associated with certain types of blood cell cancers (including lymphoma and leukemia ), although these are not the only cells involved. Basophilia is more specifically related to a group of diseases called myeloproliferative disorders, in which too many white blood cells, red blood cells, and platelets are made in the bone marrow.

This includes:

  • Essential thrombocythemia , in which too many platelets cause excessive blood clotting or bleeding.
  • Myelofibrosis , in which fibrous tissue replaces hematopoietic cells in the bone marrow, causing red blood cell deformation and anemia.
  • Polycythemia vera is a slow-growing blood cancer in which too many red blood cells are made in the bone marrow.

In addition to hypothyroidism, basophilia is associated with a wide range of autoimmune infections and inflammatory diseases , including chickenpox, smallpox, influenza, tuberculosis, ulcerative colitis, and rheumatoid arthritis.

Related to basopenia

In addition to hyperthyroidism, basopenia is seen more often in severe allergic episodes, such as drug hypersensitivity and anaphylaxis (a life-threatening whole-body allergy).

Basopenia is most often seen with hives (hives) or angioedema (severe generalized swelling of the skin).

Basopenia can also develop in the early (acute) stages of infection. Although basophilia is more common in blood cancers, basopenia can result from radiation or chemotherapy used to treat cancer.

Frequently asked questions

  • The basophil is a type of white blood cell . Although basophils are the least abundant white blood cells, they are the largest. Basophils, along with neutrophils and mast cells , are classified as granulocytes because they contain and secrete granular chemicals that help fight infection.

  • Basophils store chemicals that help coordinate the immune response . This includes histamine, which helps trigger an inflammatory response , and heparin, which prevents the blood from clotting. When summoned, basophils degranulate (break apart), releasing these chemicals.

  • Histamine, a chemical released by basophils during normal inflammation, can sometimes be released when the immune system overreacts to a harmless substance (known as an allergen ). When this happens, the rapid inflammation of the blood vessels and tissues can cause respiratory, skin and gastrointestinal allergy symptoms.

  • Basophils constitute 0.5% to 1% of the total number of leukocytes. The absolute normal basophil count, calculated by multiplying the percentage of basophils by the total white blood cell count, is 0 to 300 per microliter (μL).

  • Basophilia is an abnormally high number of basophils. Basophilia itself is not a diagnosis of any disease, but, along with other tests, it can help make a diagnosis. Possible reasons include:

  • Basopenia is a deficiency of circulating basophils. Because basophils make up such a small percentage of white blood cells, a test called flow cytometry is needed to diagnose basopenia (defined as less than 0.01 x 109 cells per liter). The reasons include:

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