Characterization of immune reconstitution of the main lymphocyte subsets following allo-HSCT. (A-F) Multicolor flow cytometry was used to enumerate CD56⁺CD3⁻ NK cells, CD3⁺ T cells, and CD19⁺ B cells in PBMC samples from allo-HSCT patients, either without (no/low EBV) or with (high EBV) high-level EBV reactivation, and from healthy controls. In each case, the left plot reports values as a percentage of CD45⁺ lymphocytes; the right plot shows the values as absolute cell numbers per microliter of blood, based on the corresponding lymphocyte counts. The solid horizontal lines represent the median values for each group. No significant differences were seen for both the NK-cell and T-cell subsets between the no/low EBV group at 3 and 6 months posttransplant and the high EBV group at the time of peak reactivation. The proportion of B cells in the high EBV group was greater than in the no/low EBV group with borderline significance (P = .079), but there was a nonsignificant increase (P = .178) in absolute B-cell numbers.