The cytoplasm of eosinophils is evenly filled by numerous orange-red granules of uniform size. They do not overlie the nucleus. The eosinophil granules contain numerous enzymes including peroxidase, phospholipase D, catalase, acid phosphatase, and vitamin B12-binding proteins.
The eosinophil's ability to kill bacteria is less than that of neutrophils. Their main purpose is to counteract parasitic infections and to participate in immune allergic reactions. They may also be increased in a variety of nonimmunologic inflammatory responses from bacteria and fungi causing chronic infections.
A high percentages of eosinophils may be present in the peripheral blood smears of patients with a variety of non-neoplastic conditions including:
- Loeffler syndrome
- Parasitic infections
Malignancies, collagen vascular diseases, and myeloproliferative disorders may also may be associated with prominent eosinophils.