B7-1 and PD-1 compete for binding to PD-L1. B7-1 and PD-1 compete for binding to PD-L1. A, 300 cells expressing a chimeric cell surface protein composed of the PD-L1 IgV domain and the TIM-3 mucin, transmembrane, and cytoplasmic domain were incubated with the indicated concentrations of anti–PD-L1 298B.8E2 for 30 minutes, followed by 2.5 μg/mL of PD-1-hIg, B7-1-hIg, or control hIg fusion proteins. Binding of fusion protein was detected with F(ab)2 anti-human IgG PE. Data are representative of two independent experiments. B, 300 hPD-L1-TIM-3 chimera–transfected cells were incubated with the indicated concentrations of B7-1-mIgG2a or mIgG2a. PD-1-hIg fusion protein was added at 2.5μg/mL. The detection reagent was F(ab)2 anti-hIgG PE. Data are representative of two independent experiments. C, 300 hPD-L1-TIM-3 chimera–transfected cells were incubated with the indicated concentrations of hPD-1-hIg or hIg. hB7-1-mIgG2a fusion protein was added at 2.5 μg/mL. The detection reagent was F(ab)2 anti-mIgG2a PE. Data are representative of two independent experiments. Apoorvi Chaudhri et al. Cancer Immunol Res 2018;6:921-929 ©2018 by American Association for Cancer Research