IL-5 receptor alpha
Summary
IL-5 receptor alpha (IL-5Rα, CD125) is the cytokine-binding subunit of the IL-5 receptor, expressed on eosinophils and basophils. It is the therapeutic target of benralizumab in eosinophilic asthma.
Detail
IL-5 is produced primarily by Th2 cells, ILC2s, and mast cells, and is the principal cytokine driving eosinophil differentiation, recruitment, activation, and survival. Its receptor is a heterodimer of a specific alpha subunit (IL-5Rα/CD125, which gives IL-5 selectivity) and the common beta chain (βc, shared with IL-3 and GM-CSF receptors). Eosinophils selectively express IL-5Rα, making it an attractive target in eosinophilic disease. Therapeutic monoclonals: mepolizumab and reslizumab bind IL-5 itself; benralizumab binds IL-5Rα and additionally engages NK cells via its afucosylated Fc to trigger antibody-dependent cellular cytotoxicity, depleting eosinophils almost completely. Indications include severe eosinophilic asthma and eosinophilic granulomatosis with polyangiitis (EGPA).
Sources
- First Aid for USMLE Step 1 2024
- Janeway's Immunobiology
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