IL5R

The interleukin-5 receptor (IL-5R) is the cell-surface receptor for interleukin-5, a cytokine that promotes eosinophil growth, differentiation, and activation. In humans, signaling is mediated by a heterodimer composed of IL-5 receptor alpha (IL-5Rα) and a shared beta chain (βc, also called IL-5Rβ or CSF2RB). IL-5R belongs to the type I cytokine receptor family.

IL-5Rα binds IL-5 with high affinity; upon ligand binding, IL-5Rα recruits the βc chain to form the signaling complex that transduces signals via JAK2 and downstream pathways such as STAT5, MAPK, and PI3K, leading to eosinophil proliferation, survival, and activation.

Expression of IL-5R is most prominent on eosinophils and their progenitors, with detectable levels on basophils and some other immune cells. The receptor is functionally important in hematopoiesis and allergic inflammation, particularly in tissues where eosinophils accumulate.

Clinically, IL-5/IL-5R signaling is central to eosinophilic diseases. Therapeutic approaches target this axis to reduce eosinophil numbers and activity. Anti-IL-5 antibodies (e.g., mepolizumab and reslizumab) inhibit the ligand, while anti-IL-5Rα antibodies (e.g., benralizumab) block signaling and can induce eosinophil depletion via antibody-dependent cellular cytotoxicity.

Research on IL-5R continues to explore its regulation, expression patterns, and potential as a biomarker or therapeutic target in eosinophil-related disorders and allergic diseases.