Eosinophils (Eos, AEC, Eo)
Eosinophils (a variety of white blood cells) are granulocytes that develop in the bone marrow. It takes eosinophils 3-4 days to mature in the bone marrow which they later exit from and migrate into the bloodstream to circulate there for a few hours. Then, they migrate from the bloodstream into the perivascular tissues, mostly into the lungs, skin and gastrointestinal tract where they may stay for up to 10-14 days.
Eosinophils are responsible for killing foreign proteins in the body. They absorb and dissolve them by means of their enzymes.
An increase in the number of eosinophils is called eosinophilia. Eosinophilia may be caused by an increased production of eosinophils by the bone marrow. This is the body’s defense mechanism in response to foreign proteins entering the bloodstream.
The most common causes for eosinophilia include allergic diseases, especially respiratory tract and skin diseases. During allergic diseases and reactions, eosinophils have transport and antitoxic functions. They are able to transport protein decay products which have antigenic properties, prevent local accumulation of antigens, and, moreover, have active phagocytic abilities.
Eosinophils play an important role in fighting helminths, their larvae and eggs. For instance, when eosinophils come in contact with larvae, they degranulate to secrete proteins and enzymes onto the surface of the larvae, and thus kill the larvae.
A decrease in eosinophils (eosinopenia) or lack of eosinophils in a volume of blood may be found during the acute stages of all acute infectious diseases.