In vivo lysis of EBV-infected B cells by EBV-CTLs. Lysis of EBV-infected B cells occurred after CTL infusion. For this purpose, free EBV-DNA was detected in the plasma by real-time PCR before and after infusion. The number of EBV-DNA copies in 200 μL plasma is shown on the y-axis. A transient increase of free EBV-DNA in the plasma was observed within 2 weeks after CTL infusion, consistent with lysis of EBV-infected B cells. Each box shows the median (bar), upper, and lower quartiles and range.