Activation of v-Abl TK reverses the loss of Ψ_m. IL-3 was withdrawn from IC.DP cells, which were then maintained at 32°C or 39°C for 18 hours and then switched to the other temperature, ie, from 39°C to 32°C or from 32°C to 39°C for a further 24 hours. (A) The percentage of cells that exclude PI at each time point. The upper two dot plots show the increase in cell death after inactivation of v-Abl TK at 18 hours compared with that observed when v-Abl TK was activated at 18 hours (lower two dot plots). (B) The changes in Ψ_m occurring before and after activation (Bi) and inactivation (Bii) of v-Abl TK. The arrow indicates the Ψ_m at 0 hours. Results are representative of three independent experiments.