Healthy EBV-seropositive patients can be distinguished from healthy EBV-seronegative patients based on production of IFNγ by PBMC in response to autologous LCL. (A) FACS dotplots of PBMC from healthy EBV-seropositive subjects 14, 22, and 26 or healthy EBV-seronegative subjects 1, 2, and 15 producing IFNγ by intracellular staining after 20 hours of culture with autologous LCL (PBMC/LCL = 5:1). (B) Comparison of percentage of PBMCs producing IFNγ between 10 healthy EBV-seropositive and 10 healthy EBV-seronegative patients after culture with autologous LCL at ratios of 10:1 or 5:1 (PBMC/LCL).