Eosinophils, or also called acidophils, are a variety of white blood cells and one of the components of the immune system responsible for fighting multicellular parasites and certain infections in vertebrates. They also control the mechanisms associated with allergy and asthma. They are granulocytes that develop during hematopoiesis in the bone marrow before migrating into the blood, after which they become terminally differentiated and do not multiply.
These cells are eosinophilic or " acidic " due to their large acidophilic cytoplasmic granules, which show their affinity for acids due to their affinity with coal tar dyes: normally transparent, it is this affinity that makes them appear brick red afterwards. of eosin staining, a red dye, using the Romanowsky method.
The stain is concentrated in small granules within the cell's cytoplasm, which contain many chemical mediators, such as eosinophil peroxidase, ribonuclease, deoxyribonucleases, lipase, plasminogen, and major basic protein. These mediators are released through a process called degranulation after eosinophil activation and are toxic to the parasite and host tissues.
In normal individuals, eosinophils constitute about 1-3% of white blood cells and are approximately 12-17 microns in size with bilobed nuclei. While they are released into the bloodstream as neutrophils, eosinophils reside in the tissue. They are found in the medulla and the junction between the cortex and the medulla of the thymus and, in the lower gastrointestinal tract, the ovary, the uterus, the spleen and the lymph nodes, but not in the lung, skin, esophagus or other internal organs under normal conditions.
The presence of eosinophils in the latter organs is associated with the disease. For example, patients with eosinophilic asthma have high levels of eosinophils that cause inflammation and tissue damage, making it difficult for patients to breathe. Eosinophils persist in the circulation for 8-12 hours and can survive in tissue for an additional 8-12 days in the absence of stimulation. Pioneering work in the 1980s elucidated that eosinophils were unique granulocytes, which have the ability to survive for long periods of time after maturation, as evidenced by ex vivo culture experiments.
