(A) Mean Bhattacharyya coefficients between the TRB repertoires of recipients at the indicated time points before or after transplant and the TRB repertoires of their related donors on the day of marrow donation. The number of donor/recipient pairs for whom a Bhattacharyya coefficient at each time point could be calculated is indicated. (B) Mean Bhattacharyya coefficients from A separated into 2 groups by donor CMV serostatus. The evolution toward a more “donor-like repertoire” over the first posttransplant year was more prominent in recipients of allografts from CMV-seropositive donors, in part due to the high frequency of CMV–specific memory T cells in both the donor and posttransplant recipient. (C) Pairwise TRB repertoire similarity matrix for donor and recipient 002-037. Both were CMV seropositive, and detectable CMV reactivation occurred in the recipient on day +41 after transplant. The donor repertoire was assessed on the day of allograft donation, and the recipient repertoire was assessed at the indicated time points before and after transplant. (D) Pairwise TRB repertoire similarity matrix for donor and recipient 002-031, who were both CMV seronegative. (E) Cumulative frequency of TRB sequences in the blood of recipient 002-037 on the indicated posttransplant days that could be presumptively mapped back to the donor’s peripheral blood (PB) repertoire. CD4⁺, CD8⁺, CD8⁺ naive, and CD8⁺ memory compartments were defined based on sorting of donor PB. The CD8⁺ CMV pp65-specific tetramer⁺ (HLA-A2– and HLA-B7–restricted) compartment was defined based on tetramer sorting of recipient samples at posttransplant days +83, +369, and +1,320. It was not possible to sort CMV pp65-specific tetramer⁺ cells from donor PB due to insufficient sample availability. (F) Cumulative frequency of TRB sequences in the blood of recipient 002-031 on the indicated posttransplant days that could be presumptively mapped back to the CD4⁺, CD8⁺, CD8⁺ naive, or CD8⁺ memory compartments of donor 002-031’s PB repertoire. (G) Venn diagram illustrating the overlap between the recipient CMV pp65 tetramer⁺ compartment and the TRB sequences that could be mapped back to the naive or memory compartment of donor 002-037, showing that nearly all CMV pp65 tetramer⁺ T cells that could be tracked were able to be traced to the memory compartment.