Foxp3⁺ Treg development is impaired during post-transplant immune reconstitution. (A) Representative FACS plots of SP CD4⁺TCRβ⁺ thymocytes in untreated and BMT mice analyzed for expression of Foxp3 and CD25, with thymocytes from BMT mice pregated on donor-derived CD45.1⁺ cells. d, day. (B–D) Quantitation of SP CD4⁺TCRβ⁺CD25⁺Foxp3⁺ Treg (B), SP CD4⁺TCRβ⁺CD25⁺Foxp3⁻ Treg precursors (C), and SP CD4⁺TCRβ⁺CD25⁻Foxp3⁺ Treg (D); white dots denote control mice, and black dots show BMT mice harvested at the indicated time points. Data from three separate experiments; n = 8 at each time point. Error bars indicate SEM. *, P < 0.05; **, P < 0.01; ***, P < 0.001; ****, P < 0.0001.