CD19/CD3 bsAb’s potentiate autologous T-cell proliferation, activation, and granzyme B expression. CLL PBMCs from treatment-naïve patients were cultured with either CD19/CD3-scFv-Fc, blinatumomab, or medium alone. To assess T-cell proliferation, PBMCs were stained with CFSE prior to culture. (A) CFSE staining in CD8 T cells from 1 representative patient after 5 and 7 days in culture. (B) CD8 and CD4 T-cell proliferation, depicted as percent decrease in CFSE MFI from the medium-only condition (n = 6). (C) Representative flow cytometry contour plots of CD25 and CD69 staining in CD8 T cells after 7 days in culture. Percent CD25⁺/CD69⁺ cells are shown. (D) CD8 and CD4 T-cell activation reported as percent CD25⁺/CD69⁺ cells after 7 days (n = 7). (E) Representative flow cytometry contour plots showing granzyme B expression in CD8 T cells after 7 days in culture. Percent granzyme B⁺ cells are shown. (F) Granzyme B expression in CD8 and CD4 T cells, reported as percent granzyme B⁺ cells, after 7 days (n = 10). For panels B and D, significance using paired Student t tests and Tukey’s multiple comparison tests are shown, respectively, along with mean and 95% CIs. For panel F, significance using Dunn’s multiple comparisons test and median and IQRs are shown, because of nonnormal distribution of data. Colors of data points in (B,D,F) correspond to colors in supplemental Table 1. *P < .05; **P < .01; ***P < .001; ****P < .0001. Grnz, granzyme.