Figure 2 Effect of MB on the proliferation of WT CTLs, PD-1KO CTLs. Splenic cells were stained with 5 μM of CFSE and seeded into aCD3/aCD28 coated 96-well plates. 10 μg/ml of PD-L1 were administered in media. Cell proliferation were checked by monitoring dilution of CFSE 48 hours after CD3/CD28 stimulation by gating on CD8 positive population through FACS analysis. WT: splenic cell from wildtype C57BL/J mice. PD-1KO: splenic cell from PD-1 knockout mice.   Statistical results of (A)   Data information: Data are representative of three independent experiments. Unpaired t-test; Error bars denote s.e.m. *P < 0.05; **P < 0.01; ***P < 0.001; ****P < 0.0001  FACS analysis of the effect of MB on the activation of OT-I CTLs. OT-I CTLs were stimulated with precoated aCD3/aCD28 and 10 μg/ml of mouse PD-L1 protein in the presence of 100 nM MB or 10 μg/ml aPD1 (served as positive control). After 24 hours, surface expression of CD25 and CD69 on OT-1 CTLs were determined through FACS analysis.   Statistical results of (C)   Data information: Data are representative of three independent experiments. Unpaired t-test; Error bars denote s.e.m. *P < 0.05; **P < 0.01; ***P < 0.001; ****P < 0.0001  Effect of MB on the activation status of Jurkat T cells. Luciferase activity is suppressed in JP-luc by co-culture with Raji-L1 preloaded with 1 μg/ml superantigen (SEE). Treatment with MB enhanced luciferase expression (SEE-Loaded Raji (PD-L1 negative) served as positive control). IC50 is calculated to be 117 nM. JP-luc: Jurkat cell harboring NFAT-luciferase transgene and overexpressing PD-1; Raji-L1: Raji overexpressing PD-L1 Data information: Data are representative of three independent experiments. Unpaired t-test; Error bars denote s.e.m. *P < 0.05; **P < 0.01; ***P < 0.001; ****P < 0.0001  Impact of MB on luciferase activity of various engineered Jurkat T cells. J-luc: Jurkat cell harboring NFAT-luciferase transgene; J-luc-sgPD-1: J-luc cells treated with lentivirus expressing sgPD-1/CAS9 simultaneously Data information: Data are representative of three independent experiments. Unpaired t-test; Error bars denote s.e.m. *P < 0.05; **P < 0.01; ***P < 0.001; ****P < 0.0001  qRT-PCR analysis of IL-2 mRNA level in JP-luc cells stimulated with precoated aCD3/aCD28 (10 μg/ml) in the presence of 10 μg/ml of PD-L1 and MB at indicated concentrations Data information: Data are representative of three independent experiments. Unpaired t-test; Error bars denote s.e.m. *P < 0.05; **P < 0.01; ***P < 0.001; ****P < 0.0001  MB enhancing IL-2 expression by JP-luc stimulated with Raji-L1 for 24-hour quantified through ELISA analysis (aPD1 served as positive control).   MB enhancing production of cytokine and cytolytic granule by OT-I CTLs. CTLs were incubated with EG7-L1 cells in the presence of protein transport inhibitor (PTI) and MB at indicated concentrations. Expression of cytokine and cytolytic granule were determined by flow cytometry. aPD1 served as positive control. EG7-L1: EG7 overexpressing PD-L1.   Statistical results of (I)   Data information: Data are representative of three independent experiments. Unpaired t-test; Error bars denote s.e.m. *P < 0.05; **P < 0.01; ***P < 0.001; ****P < 0.0001