Hematology Lessons Best Lab: Eosinophils


Background Information of Eosinophils

Eosinophils are WBCs and are one of the immune system components responsible for combating multicellular parasites and certain infections in vertebrates. Additionally they also control mechanisms associated with allergy and asthma. They are granulocytes that develop during hematopoiesis in the bone marrow before migrating into blood.

These cells are eosinophilic (ie. acid-loving) as shown by their affinity to coal tar dyes.The staining is concentrated in small granules within the cellular cytoplasm, which contain many chemical mediators, such as histamines and proteins such as eosinophil peroxidase, ribonuclease (RNase), deoxyribonucleases, lipase, plasminogen, and major basic protein.These mediators are released by a process called degranulation following activation of the eosinophil, and are toxic to both parasite and host tissues.

In normal individuals, eosinophils make up about 1-6% of WBCs.

Clinical Significance

Eosinophilia is a condition to describe an abnormal increased in eosinophils, i.e., the presence of more than 500 eosinophils/microlitre of blood and is typically seen in people with a parasitic infestation of the intestines, collagen vascular disease (such as rheumatoid arthritis), malignant diseases such as Hodgkin’s disease, extensive skin diseases (such as exfoliative dermatitis), Addison’s disease, reflux esophagitis (in which eosinophils will be found in the squamous epithelium of the esophagus), eosinophilic esophagitis, and with the use of certain drugs such as penicillin

Generally the most common cause for eosinophilia is an allergic condition such as asthma.

Cellular Description

Eosinophils are typically slightly larger than neutrophils and the presence of coarse large orange-red granules are their signature identity. The nuclear chromatin structure (nucleus) are quite synonymous to the ones found in neutrophils (ie. segmented), but is usually segmented into two swollen oval lobes.

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