BCMAxCD3 BsAb induces T-cell activation of CLL-derived T cells and leads to CLL killing. (A and B) CLL PBMCs were stimulated with 100 ng/mL BCMAxCD3, BCMAxnull, nullxCD3, or anti-CD3/CD28 antibodies. Flow cytometry analysis of CD25 (A) and CD107a (B) were performed after 4 days (n = 3–5). C, T cells from patients with CLL were isolated and cocultured in a 5:1 E:T ratio with their autologous CLL for 96 hours in the presence or absence of 100 ng/mL BCMAxCD3 BsAb and were left untreated (−) or treated with 100 nmol/L γ-secretase inhibitor (+; n = 6). The P value was calculated ordinary one-way ANOVA (A and B) or paired t test (C). Data are presented as mean ± SD. *, P < 0.05; **, P < 0.01; ***, P < 0.001; ****, P < 0.0001.