Basophils- Definition, Structure, Immunity and Functions


Basophils are a type of white blood cell that belong to the granulocyte family. Granulocytes are named after the granules they contain in their cytoplasm, which are filled with various substances that help them fight infections and inflammation. Basophils have large and dark granules that stain with basic dyes, hence the name "basophil".

Basophils are the least common type of granulocyte, accounting for only about 0.5% of the total white blood cells in the blood. They are produced in the bone marrow from stem cells and circulate in the bloodstream for a few hours before migrating to the tissues. Basophils have a short lifespan of about 60 hours and are constantly replaced by new cells.

Basophils play an important role in the immune system, especially against parasitic infections and allergic reactions. They can sense foreign substances, such as antigens, allergens, or pathogens, and release various mediators that trigger inflammation and attract other immune cells. Some of these mediators include histamine, leukotrienes, cytokines, and chemokines.

Basophils are also involved in the regulation of the adaptive immune response, which is the specific and long-lasting immunity against a particular antigen. Basophils can act as antigen-presenting cells that activate T cells and B cells, and they can also produce cytokines that influence the differentiation of T helper cells into different subsets. Basophils are particularly associated with the Th2 subset, which promotes antibody production and allergic responses.

Basophils have many similarities with mast cells, another type of granulocyte that resides in the tissues. Both basophils and mast cells have high-affinity receptors for immunoglobulin E (IgE), which is an antibody that binds to allergens and triggers degranulation. Both basophils and mast cells also release similar mediators that cause allergic symptoms, such as itching, swelling, sneezing, and wheezing.

However, basophils and mast cells also have some differences in their origin, location, morphology, and function. Basophils are derived from hematopoietic stem cells in the bone marrow and circulate in the blood, while mast cells are derived from multipotent progenitors in the peripheral tissues and remain there. Basophils have a lobed nucleus and round granules, while mast cells have a round nucleus and oval granules. Basophils can present antigens to T cells and B cells, while mast cells cannot. Basophils can also respond to other stimuli besides IgE, such as cytokines, complement components, or parasite-derived molecules.

In this article, we will explore the definition, structure, immunity, and functions of basophils in more detail. We will also compare basophils with eosinophils and mast cells, two other types of granulocytes that are involved in allergic and parasitic responses. We will also discuss the role of IgE in basophil function and the role of chitin in basophil development. Finally, we will review some of the clinical implications of basophil activation and dysfunction in various diseases.