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Basophils: An Introduction

MVSAT 2024

Basophil is a type of immune cell that contains granules with enzymes that are released during allergic reactions or asthma attacks. Basophil is a type of white blood cell and falls under the category of granulocytes along with neutrophils and eosinophils.

They are made up of a variety of substances, including histamine and heparin. As part of the body's immune defense, basophils will split open (degranulate) to release these substances when needed during an allergic reaction. These cells perform various functions to protect our bodies and there are several tests that we can do to find out the damage or any kind of disease we are suffering from.

What are Basophils?

  • White blood cells, also known as leukocytes, are of two types: Granulocytes and Agranulocytes, based on the presence and absence of granules.

  • Granulocytes are those which contain granules, like neutrophils, eosinophils, and basophils.

  • Granulocytes work together to cure illnesses or allergies in our bodies. The granules of each type of granulocyte contain a unique mix of chemicals and enzymes.

  • Basophils are the smallest granulocytes, measuring 10-14 µm in diameter.

  • These polymorphonuclear cells have a bilobed nucleus and cytoplasmic granules that are strongly metachromatic.

  • They have a short life span of 1-2 days.

  • These are the only leukocytes that circulate in the body containing histamine.

Structure of Basophil

Image: Structure of Basophil

Function of Basophils

  • Basophils are one of five types of white blood cells that protect the body against infections and respond to invaders such as parasites, fungus, and cancer cells.

  • They are a part of the innate immune system, the immunity that is present by birth.

  • The human body's reactivity to allergens is controlled by basophils.

  • Whenever we come into contact with an allergen, they're the reason we sneeze, cough, or have a runny nose.

  • They can detect and eliminate some cancer cells in their early stages.

  • During an allergic reaction or an asthma attack, basophils also release histamine from their granules, which plays a crucial role.

  • They also help in protecting our bodies against microbial pathogens, viruses, helminths, etc.

  • They are essentially the frontline cells that attack any foreign agent that makes its way into the body.

Action of Basophils

  • Basophils aid in the induction of inflammatory responses.

  • The body's natural response to anything that could harm it is known as inflammation.

  • It is the body's way of telling the immune system to heal and restore damaged tissues while also protecting itself from external invaders.

  • Histamine and heparin are among the substances found in the granules of basophils.

  • Role of Histamine: It acts as a vasodilator, which means it widens blood vessels. This attracts extra immune cells to the damage or site of infection.

  • Role of Heparin: It acts as an anti-coagulant (blood thinner). The body makes it to prevent the formation of blood clots at the site of an injury or infection.

  • Basophils also target foreign agents indirectly by binding to B-cell lymphocytes.

  • B-cells release antibodies termed immunoglobulin E (IgE) into the bloodstream as a result of the binding.

  • IgE has a high anti-parasite and anti-venom effect.

Basophils Role in Allergies

  • An allergy is when the immune system reacts abnormally to a substance or event that is otherwise safe.

  • Basophils release histamine, which is one of the main causes of allergic symptoms.

  • Basophils and related cells called mast cells break open when the body is exposed to an allergen (allergy-causing chemical).

  • Histamine causes blood vessels to dilate, allowing fluid to flow into the surrounding tissues.

  • As those tissues grow and become inflammatory, they can cause redness and swelling of the skin in the form of rashes and itching.

Levels of Basophils

  • A test called a white blood cell (WBC) count is used to determine the concentration of white blood cells, of which basophils make up between 0.5 and 1 percent.

  • The absolute basophil count (ABC) is a test that measures the actual number of basophils in cubic millimetres (mm3).

  • A basophil's normal range is 0.5% to 1% of your total white blood cell count. In healthy humans, this equates to zero to 300 basophils per microliter of blood.

  • If your basophil level is higher than this, you may have allergic reactions, chickenpox, collagen vascular disease, hyperthyroidism, or bone marrow disease.

  • The lower level of basophils indicates cancer, acute infection, and thyrotoxicosis.

  • Basophils in blood tests might be high or low in response to specific conditions or treatments.

  • Basophilia refers to an excessively high basophil count, while basopenia refers to an abnormally low basophil count.


Image: Basopenia


Basophils are granulocytes, a type of white blood cell. Basophils are one of the first lines of defense against illnesses, including parasites, as part of the innate immune system. Infections, hyperthyroidism, and chickenpox can all produce high basophilia, while acute infections and cancer treatments can all cause low basophilia. Basophils also play an important part in causing allergies by releasing histamine into the bloodstream, which is an allergy-causing substance.

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FAQs on Basophils

1. Describe the process of an Allergic Reaction.

When an allergic person is exposed to a sensitising allergen, the body produces a specific IgE that recognizes that allergen. When an allergen (antigen) enters the immune system, it binds to these IgE receptors on the cell's surface. When the allergic individual is re-exposed to the allergen that triggered the response, the IgE can bind to it. When two IgE antibodies bind to the same antigen, the interaction "wiggles" the membrane, causing the mast cell or basophil to degranulate. Degranulation refers to the breakdown of a mast cell or basophil.

2. What is the lifespan of basophils?

Basophils have a limited lifespan, which has lately been estimated to be in the range of 1–2 days. Research on basophils was initially challenging because of their life span. Basophils have been a rather perplexing immune cell type for many years, and issues about their involvement in protective immunity, as well as the infections that trigger basophil responses, remain unanswered. Because of their short life span, scientists initially thought it was of no importance but later discovered it was due to the release of histamine during allergic reactions. 

3. What is the difference between mast cells and basophils?

The common differences between mast cells and basophils are:

  • Mast cells are released from the bone marrow and mature in the connective tissue, while basophils differentiate and mature in the bone marrow only.

  • Basophils can be found circulating in the body. On the other hand, mast cells do not circulate in the body.

  • Mast cells have a larger size in comparison to the basophils.

  • Basophil has a lobed nucleus, while the nucleus of mast cells is round.

  • Mast cells are found in the connective tissue, whereas basophil is not found in any tissue and keeps circulating.

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