IL-4, IL-9, and IL-13 are not growth factors for SeAx cells. The inefficiency of IL-4 and IL-9 indicates that signals through their common receptor γ chain which they also share with the receptors of IL-2, IL-7, and IL-15 are not sufficient to sustain the growth of this cell line. The concentrations for IL-7 and IL-15 were the same ones as in Fig 1. The concentrations for IL-4 (50 U), IL-9 (50 U), and IL-13 were 90 ng/mL (100 U), 50 ng/mL, and 600 ng/mL (100 U), respectively. The molecular weights of the ILs used are 13 kD (IL-15 and IL-13), 14 kD (IL-4 and IL-9), 15 kD (IL-2), and 17 kD (IL-7). The results have been obtained from three independent experiments.