PD-1 ligands must be expressed on donor BMCs for recipient CD8 T-cell tolerance. WT or KO B6 animals were used as BMT donors with B10.S animals used as recipients of the 3 Gy/anti-CD40L/allo-BMT regimen. Dashed gray lines represent PD-L1 KO donors (A) or PD-L2 KO donors (B), while solid black lines with closed symbols represent WT control donors. CD8 depletion was performed where indicated by giving 0.72-1.44 mg of anti-CD8 (clone 2.43) intraperitoneally on day −1. 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 = 4-8 mice per group.