IL-5 and its receptor: which role do they play in the immune response?

IL-5 is a homodimeric glycoprotein that promotes proliferation and differentiation of activated B cells, and controls the production and functions of some other hematopoietic cells, such as Ly-1(CD5)+ B cells, eosinophils and basophils. In humans, IL-5 acts as a differentiation and growth factor for eosinophils, and is the major cytokine involved in the production of eosinophilia. IL-5 acts on its target cells through the specific receptor that is composed of two polypeptide chains, a and b. The alpha-chain is unique to IL-5, while the beta-chain is common to IL-5 receptor, IL-3 receptor and granulocyte-macrophage colony stimulating factor (GM-CSF) receptor.