Eosinophils
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Other Cell Types
- Neutrophils - Overview
- Neutrophils - Granules
- Neutrophils - Oxidative Burst
- Basophils
- Eosinophils
- Mast Cells
- Monocytes / Macrophages
- Natural Killer (NK) Cells
- Dendritic Cells
Summary
Eosinophils are white blood cells in the innate immune system, important in the defense against parasites (esp. worms/helminths). They are recruited and stimulated by Interleukin-5 (IL-5), and activated by antibodies bound to parasitic antigens. Once activated, eosinophils degranulate, releasing Major Basic Protein (MBP). MBP is toxic to all cells, but is extremely toxic to parasitic worms/helminths. Aberrant eosinophilic activation contributes to the pathogenesis of allergy, asthma, and certain vasculitides such as Churg-Strauss syndrome. In these autoimmune diseases, corticosteroids can be administered, since they block the activation of eosinophils.
Key Points
- Eosinophil
- Cell of the innate immune system
- Contains bilobate nucleus and eosinophilic granules
- Granules stain pink (eosinophilic) on H&E
- Recruited and stimulated by Interleukin-5 (IL-5)
- Also by eosinophil chemotactic factors (e.g. C3a and C5a)
- Activated by Fc regions of antibodies (e.g. IgE and IgG)
- Releases Major Basic Protein (MBP) when activated
- Extremely toxic to parasitic worms
- Can damage normal tissue, contributing to allergy and asthma
- Charcot-Leyden crystals in asthma are formed by degraded eosinophils
- Aberrant activation can lead to vasculitis (e.g. Churg-Strauss Disease)
- Releases Major Basic Protein (MBP) when activated
- Inhibited by corticosteroids