Antigen-specific memory T cells may survive pt-Cy and expand in the host in the presence of the cognate antigen. (A) Frequency of CMV-specific memory T cells in haplo-HSCT recipients (R) at day 45 and day 90 and in related donors (D). (B) Representative analysis of donor-derived CMV-specific T-cell responses detected by simultaneous analysis of the mismatched HLA (in this case the donor was HLA-A*02⁻) and intracellular IFN-γ following stimulation with CMV pp65 overlapping peptide mix. Plots show Aqua⁻CD3⁺ cells. (C-D) TCRB clonal composition of CMV-specific CD4⁺ (C) and CD8⁺ (D) T cells in CMV^+/+ donor/recipient pairs. Overlapping sequences are highlighted in gray. d, day after haplo-HSCT.