| Eosinophils
Definition:
Eosinophils are granulocytic immune cells strongly involved in Type-2 and
allergic airway inflammation. They release cytotoxic granule proteins,
lipid mediators, cytokines, and reactive oxygen species that can contribute
to epithelial injury and airway hyperresponsiveness.
Asthma relevance:
Elevated eosinophils are characteristic of eosinophilic asthma and are commonly
measured in blood, sputum, airway tissue, and bronchoalveolar lavage fluid
(BALF). In experimental allergic asthma, BALF eosinophil counts are one of the
most frequently reported inflammatory endpoints.
Direction:
Eosinophils ↑ = generally adverse in eosinophilic asthma
Eosinophils ↓ = generally beneficial
Common measurement contexts:
BALF eosinophils; sputum eosinophils; blood eosinophils; airway tissue eosinophils
Typical pathway:
IL-5 ↑ + CCL11 / Eotaxin ↑
→ eosinophil recruitment and survival ↑
→ airway inflammation ↑
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