Kinetics and dose-response of MoAb90-induced apoptosis. (A) Resting T cells (open symbols) or 3-day PHA-activated cells (closed symbols) were treated with control IgG1 (circles) or MoAb90 (squares) for indicated time. (B) Resting T cells (open symbols) or 3 day-PHA-activated cells (closed symbols) were treated with dose range of intact MoAb90 (squares), F(ab′)₂ fragments (circles), and Fab′ (triangles) for 24 hours. The percentage of apoptotic cells was determined by flow cytometry after staining with annexin V. Results are expressed as mean ± SD of three independent experiments.