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Published on: June 2, 2011
Characteristics of eosinophils migrating around fungal hyphae in nasal discharge
Kensuke Watanabe1, Toshihiro Misu, Shigenori Ohde
1Department of Otorhinolaryngology, Koshigaya Hospital, Dokkyo University School of Medicine, Koshigaya, Saitama, Japan.
Abstract:
It is known that eosinophil granular proteins cause tissue damage. To explore how eosinophils degranulate, we studied the degranulation of eosinophils that had migrated around fungal hyphae. In electron microscopic observations of allergic mucin from patients with allergic fungal sinusitis, fungal hyphae were detected, surrounded by numerous eosinophils. A number of eosinophils, including many disintegrated eosinophils, adhered to the cuticular layer of the hyphal surface. Although the fungal hyphae were detected in allergic mucins in all 5 patients, fungal hyphae surrounded by eosinophils were observed in only 1 patient. In the eosinophil cytoplasm, the cell membrane was invaginated, deep, and sheetlike, and the space formed by its infolding was filled with a highly electron-dense substance. This substance appeared to be a mixture of the cuticular substance of the hyphal surface and granular proteins. Thus, the eosinophil phagocytosed the cuticular substance of the hyphae into a sheetlike invaginated space, and released granular proteins into that space. The structure invaginated in the cytoplasm retained its form even after disintegration of the eosinophil, and adhered to the cuticular layer. This structure detected in eosinophils has not been reported previously, and is considered to be an interesting finding from the viewpoint of the function of eosinophils.
Insights
Eosinophils degranulate by phagocytosing fungal hyphae, releasing granular proteins. This novel mechanism, observed in allergic fungal sinusitis, involves a unique invaginated structure that adheres to fungal surfaces.
Area of Science:
- Immunology
- Cell Biology
- Mycology
Background:
- Eosinophil granular proteins are known to cause tissue damage.
- The precise mechanisms of eosinophil degranulation, particularly in response to fungal elements, require further elucidation.
Purpose of the Study:
- To investigate the degranulation process of eosinophils interacting with fungal hyphae.
- To characterize the ultrastructural changes in eosinophils during degranulation around fungal structures.
Main Methods:
- Electron microscopic examination of allergic mucin samples from patients with allergic fungal sinusitis.
- Observation of eosinophil morphology and interaction with fungal hyphae.
Main Results:
- Fungal hyphae were found surrounded by numerous eosinophils, some disintegrated, adhering to the hyphal cuticular layer.
- A novel finding revealed eosinophils phagocytosing fungal cuticular substance into a sheetlike invaginated space within the cytoplasm.
- This space contained a mixture of fungal material and eosinophil granular proteins, suggesting a unique degranulation pathway.
Conclusions:
- Eosinophils exhibit a previously unreported degranulation mechanism involving phagocytosis of fungal hyphae.
- The observed invaginated structure plays a role in releasing granular proteins and may remain adhered to the fungus even after eosinophil disintegration.
- This finding offers new insights into eosinophil function in fungal-associated inflammatory conditions.
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