TGF-β signaling into T cells is required for achievement of peripheral CD8 T-cell tolerance using anti-CD40L and allogeneic BMT. Recipients expressing a dominant-negative form of the TGFbRII specifically in T cells were given 3 Gy TBI, anti-CD40L, and allogeneic BMT and followed for development of chimerism as a readout for peripheral T-cell tolerance induction. The percentage of donor chimerism in the CD11b⁺ lineage of the peripheral blood is shown. The dotted line at 5% donor chimerism represents our cutoff for calling an animal a chimera. N = 3-6 mice per group.