Neither apoptosis nor IL-2–dependent anergy mediate Env-induced CD4⁺ T-cell suppression. PBMCs were cocultured with IIIB Env or luciferase-expressing 293T cells or 700 μM cycloheximide (CHX) and activated with 0.1 μg/mL TSST-1. Thirty-six hours later, apoptotic CD4⁺ T cells were analyzed by flow cytometry and defined as Annexin V positive and 7-AAD negative for early apoptotic cells (A) and 7-AAD positive for dead cells (B). (C) CFSE-labeled PBMCs were cocultured with IIIB Env-expressing 293T cells in the presence of 80 U/mL IL-2 and activated with 0.1 μg/mL TSST-1. CD4⁺ T-cell proliferation was measured 5 days later by flow cytometry. Quadrants labeled with percent of events in each. Experiments shown are representative of 3 independent experiments.