Scatchard transformation of saturation binding studies performed on CHO cells coexpressing (A) GMRα and full-length β_c or (B) GMRα and soluble β_c (sβ_c ). Binding assays were performed with ¹²⁵I-labeled GM-CSF over a concentration range of 10 pmol/L to 10 nmol/L. After binding had reached equilibrium, the cells were washed briefly and either lysed directly (○) or subjected to five 15-minute washes to remove ligand bound with low affinity (•). The dashed line indicates the best fit for nondissociated binding and the solid line indicates the best fit for dissociated binding.