IL-5(Interleukin-5) is a cytokine that acts as a growth and differentiation factor for both B cells and eosinophils. IL-5 plays a major role in the regulation of eosinophil formation, maturation, recruitment and survival, which are essential for mounting an effective immune response, particularly in allergic reactions and asthma. IL-5 is primarily secreted by activated T cells and acts through the IL-5 receptor, which is composed of an alpha chain that binds IL-5 with low affinity and a beta chain that forms a high-affinity receptor complex. The beta chain is shared with the receptors for interleukin-3 and granulocyte-macrophage colony-stimulating factor, highlighting the interconnectedness of these signaling pathways in immune regulation.