The major role of eosinophils is in allergic and parasitic disease, particularly helminths.
Eosinophils are activated in response to several inflammatory mediators. The most important are histamine, eosinophilic chemotactic factor A, CCL5 (RANTES) and CCL11 (eotaxin). Once activated, eosinophils mobilize their storage granules to release their contents into the tissue. Each type of granule contains different peptides, which are summarized below.
| Granule | Contents | General Function |
|---|---|---|
| Primary granules | Major basic protein | Toxic to parasites and tumour cells |
| Small granules | Acid phosphatase Other degradative enzymes | Inactivates leukotrienes; damages cell membranes |
| Large granules | Eosinophil cationic protein Eosinophil-derived neurotoxin Eosinophil peroxidase | ECP is toxic to parasites; others are microbicidal |
Although these granule contents are generally beneficial, they can also cause extensive tissue damage and collagen degradation. This is commonly seen in immune-mediated conditions like eosinophilic granulomas of cats, or allergic conditions like asthma.
Zachary JF. Pathologic Basis of Veterinary Disease, Sixth Edition.
Kumar V, Abbas AK, Aster JC. Robbins and Cotran Pathologic Basis of Disease, Tenth Edition.
Murphy KP, Janeway CA, Travers P et al. Janeway’s Immunobiology, Eighth Edition.
