A New Look at Cytokine Signaling

Signal transduction is initiated when a cytokine binds to the extracellular domains of its receptors, bringing them together and triggering a complicated sequence of events inside the cell. In this issue, present crystal structures of three signaling complexes of the cytokines interleukin-4 and interleukin-13 with their receptors, showing how events taking place outside the cell may affect the specificity of signal transduction.