Basophils serve as mediators of inflammatory responses, especially hypersensitivity reactions. IgE binds to the membrane receptors on basophils and degranulation is initiated. The enzymes released are vasoactive, bronchorestrictive and chemotactic (especially for eosinophils), so basophils seem to play a role in inducing and maintaining allergic reactions.
The granules of basophils contain histamine, heparin and peroxidase. After degranulation occurs, basophils can synthesize more granules. The release of large numbers of these granules can cause anaphylactic shock and death.
Basophils circulate in the blood for a short time and make up only a small percentage (0.5%) of the cells in circulation. They do not migrate to the tissues under normal conditions but may be seen when inflammation resulting from hypersensitivity to protein, contact allergy or skin allograft rejection is present. Basophils are sometimes increased in patients with chronic myeloproliferative disorders.