What Is a Basophil?

What are Basophils and What is Their Effect on Asthma

Basophil
What are basophils and why are they important in asthma?. "Blausen 0077 Basophil" by BruceBlaus.

Definition - Basophils

Basophils are part of your immune system that normally protects your body from infection, but can also be partly responsible for your asthma symptoms. Basophils are a type of white blood cell that are involved in inflammatory reactions in your body, especially those related to allergies and asthma. When stimulated, basophils release histamine and other enzymes that can lead to inflammation, bronchoconstriction, and asthma symptoms.

When you are exposed to allergens such as molds or animal dander, an IgE antibody binds to the allergen and stimulates the basophils to release histamine. Classic asthma symptoms follow the release of histamine.

Basophils - Function

Basophils are one of the less common types of white blood cells (around one percent of white blood cells) and are responsible for a non-specific inflammatory reaction. In response to a trigger (for example, an allergan) they release cytokines, molecular messengers which "oversee" some aspects of the inflammatory response.

With asthma and allergies, basophils in a sense "overreact" or react incorrectly, mounting an immune response when one is not needed.

As noted above, when stimulated, basophils release histamine. Basophils are part of the innate immune system which means that they mount a non-specific attack (in contrast to the "specific attack" mounted by B cells as they produce antibodies against a very specific antigen.) For example, when stimulated by a real cause (such as a virus like smallpox) or "imagined" problem (such as a piece of pollen from a tree) they secrete histamine.

This is the reason that antihistamines are often used for allergies.

Abnormal Levels of Basophils

Basophils account for roughly 0.4 to 1.0 percent of white blood cells, and are measured on a complete blood count with differential (CBC.) When the number of basophils in the body are elevated, it is referred to as basophilia.

When the number is decreased, it is called basopenia. There are very few conditions which result in a low level of basophils, primarily stress and the use of corticosteroids, but several which can result in an increase.

Basophila - An Elevated Basophil Count

Conditions which cause an elevated basophil count include primarily allergic and malignant processes. Some of these are:

  • Asthma
  • Allergies
  • Atopic dermatitis (allergic skin rash)
  • Inflammatory bowel disease:
  • Hemolytic anemia
  • Chronic myelogenous leukemia
  • Hodgkin disease
  • Hypthyroidism
  • Polycythemia vera

Basophils and the Pathophysiology of Asthma

Basophils are part of the pathophysiology of asthma and contribute to changes like inflammation and  ....bronchoconstriction that lead to asthma symptoms.

The term pathophysiology comes from the two Greek stems: 1) Pathos- meaning "suffering or disease, and 2) Physiologia- that combines physis meaning "nature" plus logos meaning "study." Thus, asthma pathophysiology is the study the underlying processes that lead to asthma symptoms and complications of the disease.

Basophils are one of the cells that increase in numbers and cause changes in the lungs that lead to symptoms. As part of the pathophysiology of asthma, basophils lead to processes that cause:

  • Increased Mucus: Irritation and inflammation in the lungs leads to production of cells that produce mucus. Thick mucus clogs the airways of your lung and makes it more difficult to breathe and increases coughing.
  • Inflammation and Swelling: When the airways of your lungs are exposed to triggers and irritants, the lungs swell in response.
  • Muscle Tightening: Smooth muscles in your airways tighten and narrow in response to your asthma attack, the airways become smaller. When the airways narrow it becomes more difficult to breathe.

Symptoms may occur quickly or may develop over a longer period of time. These symptoms include:

With appropriate treatment with targets many of the changes that are caused by basophils, progression of asthma and the long term complications may be prevented. Over time poorly controlled asthma leads to remodeling and may lead to permanent changes or damage to the lungs. Poor control primarily results from inadequate treatment—either not being prescribed enough medication to control the changes seen in the pathophysiology of asthma or not sticking to your treatment regimen as prescribed.

Basophils and Asthma - A Different Perspective

As happens so often in medicine, the role of basophils in asthma has recently been questioned. In fact, its now thought by some that rather than being a detriment in asthma, basophils may even have a protective effect in some circumstances, by modulating some parts of the cycle of both innate (non-specific) and acquired (specific) immune system. As our understanding of the immune system and immunotherapy improves, it's likely that our understanding of basophils in the inflammation behind allergies will improve substantially.

Clinical Basophil Testing (BAT) and The Future

As our understanding of the molecular basis of asthma, allergies, and the role of cells such as basophils improves, it's also likely that new treatments will become available that better address the diagnosis and monitoring of allergies and asthma. For example, a 2016 study found that physicians may look for activation of basophils in the bloodstream to see if a reaction is due to a drug induced allergy (drug induced anaphylactic reaction) or some other process. There is still debate and controversy over what role monitoring basophil levels have, however, in the routine diagnosis and management of asthma and allergies.

Sources:

Hoffmann, J., Knol, E., Ferrer, <. Et al. Pros and Cons of Clinical Basophil Testing (BAT). Current Allergy and Asthma Reports. 2016. 16(8):56.

Kim, S., Kim, J., Jang, Y. et al. The Basophil Activation Test Is Safe and Useful for Confirming Drug-Induced Anaphylaxis. Allergy, Asthma, and Immunology Research. 2016. 8(6):541-4.

Siracusa, M., Kim, B., Spergel, J., and D. Artis. Basophils and Allergic Inflammation. Journal of Allergy and Clinical Immunology. 213. 132(4):789-801.

Continue Reading