[2] They also produce compounds that coordinate immune responses, including histamine and serotonin that induce inflammation, and heparin that prevents blood clotting,[3] although there are less than that found in mast cell granules.

However, they arise from different branches of hematopoiesis, and mast cells usually do not circulate in the blood stream, but instead are located in connective tissue.

Basophils have protein receptors on their cell surface that bind IgE, an immunoglobulin involved in macroparasite defense and allergy.

It is the bound IgE antibody that confers a selective response of these cells to environmental substances (e.g., pollen proteins or helminth antigens).

Recent studies in mice suggest that basophils may also regulate the behavior of T cells and mediate the magnitude of the secondary immune response.

When activated, basophils degranulate to release histamine, proteoglycans (e.g. heparin and chondroitin), and proteolytic enzymes (e.g. elastase and lysophospholipase).

Interleukin-4 is considered one of the critical cytokines in the development of allergies and the production of IgE antibody by the immune system.

Especially, in the diagnosis of allergies including of drug reactions (e.g. induced by contrast medium), the BAT is of great impact.

[17] Basophils are easily isolated from venous blood and present good "indicator cells" of an IgE-mediated allergic response based on the upregulation of activation markers such as CD63 and/or CD203c upon suspect allergen stimulation.