Figure 1.

(a) Cytoplasmic domains of the mutant IL-5Rα used in this study, and comparison of the amino acid sequence of cytoplasmic domains of murine IL-5Rα, IL-3Rα, and GM-CSFRα. Deleted residues are shown by hyphens. Shaded boxes with TM represent the transmembrane portion. (b) IgM secretion of BCL1 transfectants expressing the chimaeric receptors between IL-3Rα and IL-5Rα. Transfectants were incubated for 5 days in the presence of IL-3 (100 U/ml) and IL-5 (100 U/ml), and the IgM secreted in culture supernatants was titrated. The results were expressed as mean IgM (µg/ml) of triplicate cultures. Three independent clones were examined and similar results were obtained.