AMG 701 specifically induced proliferation of patient T cells cocultured with MM cells, more prominently in CD8 vs CD4 subsets. (A) Purified patient T cells were labeled with CTV and cocultured with RPMI8226 MM target cells (E:T = 3:1) in the presence of AMG 701 for 4 days, followed by quantitative FC analysis to evaluate the percentage of proliferative (CTV-diluted or CTV⁻) CD4 and CD8 T subsets (left panels). CD25 and CD69, as late and early activation markers, respectively, were also examined in the proliferative T-cell subsets (right panels). (B) Indicated MM target cell lines (n = 3) were coincubated with CTV-labeled patient T cells (n = 3) at 2 indicated E:T ratios in the presence of AMG 701 (0, 9.3, 93.4 pM). Data are shown as the percentage of CTV-diluted (means ± SDs) in CD4 and CD8 T subsets. Three independent experiments were done with T cells from 3 patients. Each experiment was performed in triplicate at each condition. *P < .05; **P < .005; ***P < .001; ****P < .0001.