Interleukin-5.

Interleukin-5 is a dimeric cytokine that controls the differentiation of B cells into antibody-secreting cells as well as inducing the growth of Ly-1(CD5)+ B cells and B-cell tumors. It also has a major role of the growth and differentiation of eosinophils. Rapid progress has been made during the last year in the delineation of the structure and activities of interleukin-5, and the molecular nature of its functional receptors. Interleukin-5 exerts pleiotropic activities on various target cells through a high-affinity receptor which is composed of two different polypeptide chains, alpha and beta. The alpha chain binds interleukin-5 with low affinity and the beta chain has been identified as the interleukin-3 receptor-like protein and is also the beta chain of the granulocyte-macrophage colony stimulating factor receptor.