Figure 5.

TCR/PD-L1 activation in the presence of CD28 costimulation results in inhibition of T cell proliferation. Purified human CD4⁺ cells were stimulated for 4 d with anti-CD3 mAb/control mIgG–coated beads (gray bars), or anti-CD3 mAb/hPD-L1.Ig(γ2a)–coated beads (black bars) in the presence of various concentrations of soluble anti-CD28 mAb. Stimulations were performed at (A) suboptimal (1 μg/ml) and (B) optimal (2 μg/ml) concentrations of anti-CD3 Ab. The bead/cell ratio was 1:1. Proliferation was determined by [³H]thymidine incorporation in triplicate wells. The data are representative of two separate experiments.