-Interleukin 5 receptor (IL-5R) complex comprises an IL-5-binding protein, commonly referred to as IL-5Rα (CD125), and a ß-chain (CD131) (56). -CD125 is crucial for eosinophil proliferation, immune responses activation, and survival in response to IL-5 (104). - Involved in allergic immune responses and eosinophilic disorders, such as asthma eosinophilic esophagitis, hypereosinophilic syndrome and allergic rhinitis, making it a target in the treatment of eosinophilia-associated disorders. The gene discussed is CSF2RB; the disease is eosinophil disorder.