UPN 440 developed EBV-LPD 9 weeks after an unrelated, T-cell–depleted SCT. Levels of EBV DNA determined by semiquantitative PCR are presented on the top panel (A). Two weeks after receiving a donor leukocyte infusion, this patient had a decrease in levels of EBV DNA (B). There was a progressive increase in the amount of EBV-specific cytotoxicity against the donor BLCL, which had reached normal levels at 2 weeks postinfusion (C). This correlated with the development of normal levels of EBV-specific, cytotoxic T-cell precursor frequencies. This patient died from graft-versus-host disease.