Figure 4.

TCR activation of murine and human T cells in the presence of PD-L1 results in inhibition of T cell proliferation and cytokine production. (A) Splenic T cells from wild-type (open squares) and PD-1 ^−/− (filled circles) C57BL/6 mice were stimulated for 72 h with varying concentrations of precoated anti-CD3 Ab. (B) Splenic T cells from wild-type (squares) and PD-1 ^−/− (circles) C57BL/6 mice were stimulated for 72 h with 10 μg/ml of anti-CD3 mAb in combination with varying concentrations of hPD-L.Ig(γ2a) (filled symbols) or control mIgG2a (open symbols). [³H]Thymidine incorporation was measured in triplicate. These data are representative of four separate experiments. (C) Purified human CD4⁺ T cells were stimulated for 4 d with anti-CD3 mAb/control IgG–coated beads (stippled bars), anti-CD3 mAb/hPD-L1.Ig(γ2a)–coated beads (hatched bars), or medium alone (black bars). The bead/cell ratio was 1:1. Proliferation was determined by [³H]thymidine incorporation in triplicate wells. Supernatants were collected at 96 h after activation, and cytokine concentrations were measured using commercially available ELISA kits. The data are representative of two separate experiments.