éosinophile

An eosinophil is a type of white blood cell, a granulocyte, and a key component of the immune system. They are characterized by their large, eosinophilic (readily stained by eosin dye) granules, which give them their name. Eosinophils are produced in the bone marrow and circulate in the blood before migrating to tissues throughout the body. Their primary role is to combat parasitic infections and modulate allergic inflammatory responses.

When an eosinophil encounters a parasite, it releases the contents of its granules, which can be toxic to the organism. In allergic reactions, eosinophils contribute to inflammation by releasing mediators that cause symptoms such as itching, swelling, and bronchoconstriction. They are also involved in the pathogenesis of certain chronic inflammatory conditions, including asthma, eczema, and allergic rhinitis. The number of eosinophils in the blood, known as the eosinophil count, can be elevated in various conditions, serving as a diagnostic marker. Low eosinophil counts are generally not considered clinically significant unless associated with specific medical circumstances.