CD124. also known as the interleukin-4 receptor alpha chain (IL-4Rα), is a key component of the type I and type II IL-4 receptors. It pairs with the common gamma chain (γC) to form the type I receptor, which binds IL-4. or with IL-13Rα1 to form the type II receptor, enabling responses to both IL-4 and IL-13. These receptors are critical for signaling in immune cells, including T cells, B cells, and mast cells, regulating processes like Th2 differentiation, antibody class switching, and allergic inflammation. CD124 antibodies are tools designed to target this subunit, either to block IL-4/IL-13 signaling or to study receptor expression and function. In research, they help dissect Th2-mediated immune pathways linked to allergies, asthma, and autoimmune diseases. Therapeutically, anti-CD124 agents (e.g., dupilumab, a monoclonal antibody targeting IL-4Rα) are used to dampen pathological immune responses in conditions like atopic dermatitis and eosinophilic disorders. CD124 antibodies also serve diagnostic roles, identifying receptor expression on malignant cells in certain lymphomas or leukemias. Their development underscores the importance of IL-4/IL-13 signaling in health and disease, offering insights into targeted immunomodulation strategies.