Interleukin 5 (IL-5), also known as eosinophil differentiation factor (EDF) or eosinophil colony stimulating factor (Eo-CSF), belongs to the hematopoietic family of cytokines, together with IL-3 and GM-CSF, whose receptors share the common-cytokine-receptor β-chain. IL-5 is secreted by T helper cells, mast cells, and eosinophils and mainly acts as a key hematopoietic growth factor for the proliferation and activation of eosinophils, but also promotes the secretion of immunoglobulins by B cells, and the generation of cytotoxic T cells. Through the activation of eosinophils, IL-5 mediates several allergic diseases, but it is also involved in parasitic infections and tumor development.
