FCs induce Treg generation in vivo. Purified B6 HSCs and NOD HSCs were mixed with B6 FCs, administered to ablatively conditioned NOD recipients, and Treg generation was evaluated. (A) Experimental design for the induction of in vivo Treg generation. (B-D) Representative analysis of donor or recipient CD8⁻/CD4⁺/CD25⁺/FoxP3⁺ Tregs in chimeric spleen, thymus, and bone marrow at 5 weeks after transplantation. (E) Kinetics of absolute number of donor or recipient Tregs in chimeric spleen, thymus, peripheral blood, and bone marrow at 2, 3, 4, and 5 weeks after transplantation. Results are from 4 separate experiments (n = 4).