1. Develop in marrow
Eosinophil precursors mature in bone marrow, supported by signals including IL-5.
IMMUNE CELLS
Eosinophils
Granules. Signals. Tissue Adaptation.
Eosinophils are granulocytes with a bilobed nucleus and distinctive protein-rich granules. They participate in type 2 immune responses, interact with parasites and help regulate tissue environments. When their responses are excessive or persistent, they can contribute to inflammation and tissue injury.
Back to all innate immune cells →What Are Eosinophils?
Eosinophils develop in the bone marrow and circulate in blood before entering tissues. Their orange-red staining granules contain proteins such as major basic protein and eosinophil peroxidase. IL-5 is an important signal for their development, survival and activation.
Many eosinophils reside in tissues, particularly the gastrointestinal tract. They release cytokines, lipid mediators and granule contents, with effects that depend on location and activation. They contribute to some allergic diseases, but their roles extend beyond allergy.
How Eosinophils Reach and Respond in Tissues
Development, recruitment and local activation shape eosinophil activity.
2. Enter tissues
Chemokines and adhesion molecules guide recruitment from blood into tissues.
3. Integrate signals
Cytokines, receptors and the local environment shape survival and activation.
4. Deliver mediators
Cells selectively release granule proteins, cytokines and lipid mediators.
Key Functions of Eosinophils
Specialized cellular functions contribute to coordinated immunity.
1. Participate in defense
Eosinophils interact with some helminths; effects differ with parasite and setting.
2. Coordinate immunity
Cytokines and other mediators influence nearby immune and tissue cells.
3. Support tissue homeostasis
Tissue-adapted eosinophils participate in regulation, especially at mucosal sites.
4. Influence remodeling
Interactions with epithelial and stromal cells can affect repair and matrix turnover.
Key Takeaways
- Eosinophils are granule-rich cells with a bilobed nucleus.
- IL-5 is important in eosinophil biology.
- Most eosinophil activity occurs within tissues.
- Roles include immune signaling and tissue regulation.
- Persistent activation can contribute to tissue injury.
- Cell counts do not capture every aspect of eosinophil function.
Eosinophils and Aging
Age-associated effects vary across eosinophil functions and clinical contexts.
- Some studies report altered granule-protein release.
- Chemotaxis and other responses may remain preserved.
- Tissue conditions influence survival and activation.
- Disease, medications and exposures affect measurements.
- A blood count alone does not define age-related function.
Selected sources and references
- IgE, mast cells, basophils and eosinophils
- Innate immune changes with age
- Spatial adaptation and eosinophil functions
- Tissue-resident eosinophils
- Eosinophils and airway remodeling
- Intestinal eosinophils
Artwork illustrates the main mechanisms schematically; molecular sizes, colors and distances are not literal.