Phenotypic analysis of donor CMV ORF-specific memory T-cell responses in relation to CMV reactivations and magnitude of the corresponding responses in the recipient after HSCT. (A) For donor ORF-specific T-cell populations that were less differentiated (CD27⁺CD45RO⁺CD57⁻), there was a greater probability of persistence and expansion (increased fold change) in the recipient after HSCT. For donor ORF-specific T-cell populations that were more differentiated (CD27⁻ memory; CD27⁻CD57⁺ memory), there was a greater probability of contraction (decreased fold change) in the recipient after HSCT. (B) In donors with a higher frequency of CD8⁺ CMV-specific CD27⁺ memory T-cell responses, fewer CMV reactivations were observed in the recipient after HSCT. Conversely, in donors with a higher frequency of more differentiated CD8⁺ CMV-specific memory T-cell responses (CD27⁻), a greater number of CMV reactivations were observed in the recipient after HSCT. No correlations between the phenotype of donor CMV-specific CD4⁺ T cells and the incidence of CMV reactivation in the recipient after HSCT were observed. The patients who reactivated CMV are shown in Table 1.