Loss of molecular shield is associated with increased efficacy of anti-CD137 mAb therapy. Groups of 10 DBA/2 mice were given subcutaneous injections of 5 × 104 mock/P815, B7-H1/P815 or ΔB7-H1/P815 cells on day 0. Mice were then treated intraperitoneally with 200 μg control IgG or anti–mouse CD137 mAb (clone 2A) at days 7 and 10. Each point is the mean of 10 with SD. The data are representative of at least 3 experiments.