Changes in phenotype and cytokine production of CMV ORF-specific T cells in the donor and recipient after HSCT. (A) Phenotype of CMV ORF-specific responses in donors and recipients after HSCT. Matched ORF-specific responses to CMV acquired a more differentiated phenotype after HSCT, with significant increases in both CD27⁻ memory and CD57⁺ memory T-cell populations in both the CD4⁺ (left panels) and CD8⁺ (right panels) subsets; similarly, significant decreases were observed in the corresponding CD27⁺ memory T-cell populations. (B) Analysis of the contribution of each cytokine and CD107a to the increment in CMV-specific T-cell responses after HSCT is shown in the upper panels. Each of the 5 independent functions was analyzed for each ORF-specific T-cell response after HSCT and compared with the corresponding response in the donor. For CD4⁺ T-cell responses, IFN-γ secretion increased in the recipient after HSCT (P = .024); for CD8⁺ T-cell responses, an increment in CD107a mobilization and the production of IFN-γ, MIP-1β, and TNF-α was observed in the recipient after HSCT. When T-cell responses were categorized on the basis of the number of functions elicited on CMV antigen encounter (bottom panels), bifunctional responses increased within both the CD4⁺ and CD8⁺ subsets after HSCT (P = .017 and P = .003, respectively). The median is depicted in red. Only frequencies ≥ 0.01 are shown for graphical representation. D indicates donor; and R, recipient after HSCT. *P < .05, **P < .01 (Mann-Whitney U test).