IL-13 and IL-4 share signal transduction elements as well as receptor components in TF-1 cells

IL-13 and IL-4 are growth factors for the human erythroleukemia cell line TF-1. In these cells both cytokines share overlapping binding sites, but the number of sites for IL-13 is half of that for IL-4. Two monoclonal antibodies against the extracellular domain of the IL-4R alpha chain completely abolish the binding of IL-13, although IL-13 does not bind to this chain. Following receptor triggering, IL-13 and IL-4 induce the phosphorylation of a 170 kDa protein, probably the IL-4-induced phosphotyrosine substrate. In addition the phosphorylation of the 170 kDa protein results in its tight association with phosphatidylinositol-3-kinase.