What are Basophils?

Basophils are a type of white blood cell. Basophils work closely with your immune system to defend your body from allergens, pathogens and parasites. 

Basophils have a short life span, usually only one or two days.

Basophils are mononuclear cells, so they have one round nucleus. Basophils are also granulocytes, or white blood cells that have granules, or small particles, attached to them. These small particles are filled with enzymes, like histamine, that are released during allergic reactions. Basophils are the only white blood cells circulating around your body that contain histamine. During an allergic reaction, histamine is responsible for many of the typical symptoms of allergies, like a runny nose or sneezing.

Histamine is a vasodilator. This means it widens the blood vessels near an infection to open and allow more blood flow to the site of the infection. Heparin is a naturally occurring blood thinning substance which prevents clotting.

Basophils are responsible for the body’s immune response during allergic reactions. When the body is exposed to an allergen, basophils release histamine which triggers the physical symptoms of an allergic reaction. This causes the typical allergic reaction of running nose, watering eyes etc.

They also help to produce a crucial antibody called immunoglobulin E (IgE). Immunoglobulin attaches to basophils and a similar type of cell called mast cells. The cells then work together to release histamine and serotonin, which affects the inflammatory response to the allergen.

What are white blood cells and where do Basophils fit in?

White blood cells are made inside your bone marrow and can be found in your blood and lymph tissues. White blood cells help your body fight off infections and illnesses.

There are three types of white blood cells, each with its own function to boost your immune system, including granulocytes, monocytes and lymphocytes.

Basophils are one of three granulocytes, along with neutrophils and eosinophils. Basophils are the smallest in number of granulocytes but the largest in cell size. Basophils play an important role helping your body respond to allergic reactions.

Other types of granulocytes include:

Neutrophils: This is the largest group of white blood cells in your body. They help fight infections.

Eosinophils: These help cells combat parasite infections. Like basophils and mast cells, they play a role in allergic reactions, asthma, and fighting parasite pathogens. They also develop in the bone marrow before moving into your blood.

The other main types of white blood cells are:

Lymphocytes: These cells are part of your immune system. They attack pathogens, including bacteria and viruses.

Monocytes: These cells are part of your immune system. They fight infections, help remove damaged tissues, and destroy cancer cells.

What do Basophils do?

Basophils release enzymes to improve blood flow and prevent blood clots.

Basophil cells are unique in that they don’t recognize pathogens they've already been exposed to. Instead, they attack any organism they see that is unfamiliar to your body. Basophils destroy foreign organisms by surrounding and ingesting them (phagocytosis).

Basophils function to defend your body against:

- Allergens

- Bacterial, fungal and viral infections (pathogens)

- Blood clotting

- Parasites

Let's talk more about the enzymes histamine and heparin that basophils can release:

During allergic reactions, basophils release two enzymes, histamine and heparin.

The granules of basophils hold both histamine and heparin. When a foreign organism enters your body, your basophils activate and release these enzymes to assist your immune system’s response to destroy the organism.

What does histamine do?

Histamine enlarges your blood vessels to improve blood flow and heal the affected area. Histamine opens pathways for other cells in your immune system to quickly target and respond to the allergen. You can identify when your basophil cells release histamines because you will experience physical symptoms of an allergic reaction like itchy skin, a runny nose and watery eyes.

What does heparin do?

Basophils also release an enzyme called heparin that prevents blood from clotting too quickly.

Where are basophils located?

Basophils form in the soft tissue of your bones (bone marrow). After the cells mature, they travel through your bloodstream and migrate to damaged tissues to help heal the area after an injury.

How many basophils are in my body?

White blood cells make up approximately 1% of all the cells in your body. Basophils are the smallest in quantity and make up less than 1% of all white blood cells.

What is the normal range for basophils?

Of all your white blood cells, basophils are some of the fewest in number, at only 0–1% of the total white blood cell count. 

On a laboratory report, the typical range of basophils will be 0.0–0.2 thousand cells per cubic millimeter (K/cumm or x10E3/uL). Anything above 0.2 x10E3/uL could indicate an underlying medical condition. 

A blood test is the only way to see your basophil levels. Typically, this test is part of a routine blood test called a complete blood count (CBC). When basophil levels are not within the typical range, it may indicate a basophilic disorder.

Additional note on your results:

You can expect some degree of variability between different laboratories as they might use different equipment, machines and tools to analyze your blood. Do not jump to conclusions if your results are slightly out of range. As long as it’s in the normal range based on the laboratory that did the testing, your value is normal. Your doctor will interpret your values in conjunction with your medical history and other test results. It is always advisable to not rely on one single test result to make a diagnosis. Results van vary from day to day and looking at the trend can be beneficial. 

References:

-- Eosinophils, mast cells, basophils: friends, foes, or both?  worldallergy.org/eosinophils-mast-cells-and basophils/eosinophils-mast-cells-and-basophils.php

-- Learn about the five common white blood cells. uwosh.edu/med_tech/what-is-elementary-hematology/white-blood-cells

-- Mayo Clinic Staff (2016, Nov 2). Myelofibrosis mayoclinic.org/diseases-conditions/myelofibrosis/home/ovc-20261141

-- Mayo Clinic Staff (2015, June 24). Essential Thrombocythemia mayoclinic.org/diseases-conditions/thrombocythemia/basics/definition/con-20034386

-- Mayo Clinic Staff. (2014, July 9). Pediatric white blood cell disorders: Definition mayoclinic.org/diseases-conditions/pediatric-white-blood-cell-disorders/basics/definition/con-20036078

-- Mayo Clinic Staff. (2014, April 10). Polycythemia Vera mayoclinic.org/diseases-conditions/polycythemia-vera/basics/definition/con-20031013

-- Stone, K. D., Prussin, C., & Metcalfe, D. D. (2010, February). IgE, mast cells, basophils, and eosinophils. Journal of Allergy and Clinical Immunology, (152)2 Suppl 2, S73-S80 ncbi.nlm.nih.gov/pmc/articles/PMC2847274/

-- WBC Differential. Lab Tests Online. (2015, December 3) labtestsonline.org/understanding/analytes/differential/tab/test

-- Blood differential test Information | Mount Sinai - New York. Mount Sinai Health System. Accessed June 15, 2021. https://www.mountsinai.org/health-library/tests/blood-differential-test