Induction of apoptosis by withdrawal of IL-3 from IC.DP and IC2.9 cells. (A) Kinetics of cell death of IC2.9 cells (triangles) and IC.DP cells (squares) after withdrawal of IL-3 measured by trypan blue exclusion. Cells were maintained at either 32°C (open symbols) or 39°C (solid symbols). Data points are the mean value ± SEM of three repeated experiments. (B) Flow cytometric analysis of apoptosis in IC.DP and IC2.9 cells maintained at either 32°C or 39°C for 18 hours after withdrawal of IL-3 determined by binding of annexin V and uptake of propidium iodide. Results are representative of three repeated experiments.