LAG-3 blockade prevents development of long-term CD8 T-cell tolerance. WT B6 animals were used as recipients of 3 Gy TBI/anti-CD40L/allo-BMT with or without administration of blocking anti–LAG-3 mAb. CD8 depletion was performed where indicated by giving 0.72-1.44 mg of anti-CD8 (clone 2.43) intraperitoneally on day −1. Dashed gray lines represent animals receiving blocking anti–LAG-3, while solid black lines represent control animals not treated with anti–LAG-3. The percentage of donor chimerism in the B-cell lineage of the peripheral blood is shown. The dotted line at 5% donor chimerism represents our cutoff for calling an animal a chimera. N = 7-8 mice per group.