Binding characteristics of sIL-11R. (A) Effect of IL-11 concentration on specific binding of ¹²⁵I-labeled sIL-11R (2 × 10⁵ cpm) to 10⁶ M1 cells. (B) Scatchard analysis of sIL-11R binding to M1 cells in the presence of IL-11 (50 nmol/L). (C) Effect of ¹²⁵I-labeled IL-11 (1.5 nmol/L) binding to 10⁶ M1/IL-11R cells in the absence (□) or presence () of 30-fold excess of unlabeled IL-11. Results are mean and standard deviation of duplicate measurements.