IL-2/IL-2 receptor signaling prevents Tregs from undergoing activationinduced cell death. Treg and Tcont cell lines were rested or stimulated with anti-CD3/CD28–coated dynal beads for 3 days, or with anti-CD3/CD28–coated dynal beads and IL-2 as described in Figure 3. (A) Viability was analyzed at day 3 by annexin V and PI staining. Numbers represent percent of cells double negative for annexin V and PI. (B-C) Cell lysates from the same samples were analyzed by SDS-PAGE and immunoblot with indicated antibodies. Results are representative of 3 independent experiments.