Levels of CMV pp65-specific IFN-γ–CD8⁺ in PBMC samples from R⁺ HCT recipients. The circles are average percentages of IFN-γ–CD8⁺ within PBMC samples from R⁺ HCT recipients in response to stimulation with CMV pp65 peptide library. All measurements from day 90 to day 360 were pooled together and divided into 4 groups according to donor CMV status and CMV reactivation post-HCT assessed by quantitative PCR (“Prospective study subjects”). The D⁻/R⁺ prereactivation group had significantly lower values compared with the other groups (P < .001, see Table 4). Within the prereactivation subset, D⁻ has significantly lower levels than D⁺ (P = .002, adjusted as in Table 4, P < .001 unadjusted). The effect of donor status was significantly different in prereactivation versus postreactivation samples (P < .001 interaction test, adjusted as in Table 4). Each dot represents a single IFN-γ measurement. The lower and upper horizontal border of the box drawn for each group marks the 25th and 75th percentiles, with a solid bar at the median and whiskers covering the range of the data. Horizontal scatter within boxes is introduced to avoid overlap. Pre-R and post-R refers to CMV reactivation.