Blockade of B7-H1 or PD-1 reverses established T-cell anergy. B6 mice were given OT-1 cells prior to intravenous administration of 0.5 mg OVA peptide. On day 10 after OVA peptide injection, mice were given 100 μg intravenously of control hamster IgG, B7-H1 mAb (clone 10B5), or PD-1 mAb (clone G4) together with (A) or without (B) intravenous administration of 0.5 mg OVA peptide. Blood was taken from mice at the time points indicated, and the percentage of OT-1 cells observed in each mouse was analyzed by flow cytometry as described previously. The data shown are the means ± SD of 3 mice in each group and are representative of at least 3 independently performed experiments.