Magnitude of recipient CMV-specific T-cell responses correlates with the abundance of CMV-specific T cells in the donor. (A) Counts of CMV-specific T cells in CMV-reactivating patients who underwent haplo-HSCT and received or did not receive CD45RA-depleted DLI (n = 9-16/group). Medians with interquartile range are shown. Statistical significance was determined with Mann-Whitney test. (B) Effector functions of CMV-specific CD8⁺ T cells in patients who underwent haplo-HSCT and received or did not receive CD45RA-depleted DLI, and in CMV⁺ healthy controls (n = 6-20/group in pie charts, n = 10-20/group in bar graphs). Samples containing <35 CMV-specific CD8⁺ T cells were excluded from analysis. Medians are shown. Statistical significance was determined by Kruskal-Wallis and posthoc Dunn’s test with Bonferroni correction. (C) CMV-specific CD8⁺ T cell PhenoGraph cluster identities are revealed by balloon plot, whereas the heatmap shows median cluster dynamics in CMV-reactivating patients who received DLI (n = 17), their donors (n = 16), and CMV⁺ healthy controls (n = 12). Samples containing <50 total CD8⁺ T cells were excluded from temporal analysis. (D) Linear regression with 95% confidence interval bands on the maximum measured abundance of CMV-specific T cells in the patients who received DLI vs the frequency of CMV-specific T cells in the peripheral blood of the donor. Only patients with a clear CMV-specific T cell response are included in the analysis (n = 12; one patient was excluded because of missing donor sample). Count values were log-transformed. HC, healthy control; Multif, multifunctional; T_CM, central memory T cell; T_EF, effector T cell; T_EM, effector memory T cell; T_EMRA, effector memory T cell re-expressing CD45RA.