Persistence and memory differentiation of antigen-specific T_N. (A) Frequency of CD8⁺ T cells in PBMCs from 2 CMV⁻ donors and matched CMV⁺ recipients at different time points post–haplo-HSCT. (B) Frequency and phenotype of MART-1– and WT1-specific CD8⁺ T cells identified by MHC class I tetramers. Tetramer⁺ T cells are overlaid on top of the total CD8⁺ T-cell population depicted in gray. In panels A and B, numbers indicate the percentage of cells identified by the gates. (C) Frequency of MART-1⁺ (filled gray circles) and WT1⁺ (blank circles) CD8⁺ T cells with a T_N-cell phenotype in donors (D) and recipients (R) at day 45 and day 90 post–haplo-HSCT. P < .05, Mann-Whitney test. (D) Mean ± SEM frequency of the cells identified in panel B.