[Growth and differentiation of eosinophils--special reference to IL-5 and its receptor]

IL-5 is a 46 KDa glycoprotein secreted from activated T cells, and plays an important role both in the growth and production of eosinophils. Murine eosinophils have been reported to express high and low affinity receptors. The IL-5 receptor is composed of two membrane protein subunits, alpha and beta subunits. Both alpha and beta chain of mouse and human IL-5 receptor have been identified and sequenced. The alpha subunit is a 60 KDa protein which binds to IL-5 with low affinity. The beta subunit is a 130 KDa protein which does not bind to IL-5 by itself, but forms the high affinity IL-5 receptor in the presence of the alpha subunit. On the other hand, only a high affinity receptor population has been identified on human eosinophils. Affinity cross-linking experiments resulted in the identification of human IL-5 receptor on eosinophils with a molecular mass of 55-60 KDa.