ABSTRACT
The production of eosinophils can be influenced by various cytokines, including interleukin-5 (IL-5) and granulocyte-macrophage colony-stimulating factor. There is ample evidence that IL-5 plays a crucial role in both in vitro and in vivo assay systems in eosinophilopoiesis in a lineage-specific manner. IL-5 is a T-cell-derived glycoprotein that stimulates eosinophil colony formation and growth and differentiation of eosinophils. Multiple cytokines including IL-5 control cells in any one lineage and are active on cells of more than one lineage. This redundancy and pleiotropy of cytokines are explained by two processes. The first is interaction at the ligand-receptor level. Individual cells in each lineage simultaneously display receptors for more than one growth factor. The second process is cross-talk at the intracytoplasmic level for the signal transduction cascade. The IL-5 signal can be transduced through the high-affinity IL-5 receptors and consist of two different polypeptide chains; alpha and beta.
