The binding of BION-1 to TF1.8 cells is inhibited by IL-3 but not by TNF. TF1.8 cells (2 × 10⁶) were incubated with a range of concentrations of IL-3 (•) or TNF (○) in the presence of ¹²⁵I-labeled MoAb BION-1 (1 nmol/L). Each point is the mean of duplicate determinations and error bars represent 1 standard deviation.