BION-1 blocks IL-5–, GM-CSF–, and IL-3–induced survival of eosinophils. (A) The percentage of viability of eosinophils after 36 hours in the presence of a range of concentrations of IL-5 (▪), GM-CSF (•), IL-3 (▴), or MoAb BION-1 (◊). (B) The percentage of viability of eosinophils after 36 hours in the presence of IL-5, GM-CSF, and IL-3 (1 nmol/L) and different concentrations of MoAb BION-1 (open symbols) and a control anti-β_c MoAb, 8E4 (solid symbols). Each point is the mean of triplicate determinations and error bars represent 1 standard deviation.