LMP1-specific CTL lines recognize the HLA-A2–restricted LMP1 epitope YLQQNWWTL (YLQ).

The ability of T cells in PBMCs, EBV-specific CTLs, and LMP1-specific CTLs to secrete IFN-γ in response to the LMP1 peptide YLQ was determined in ELISPOT assays. Spot-forming cells (SFCs) were quantified by Zellnet Consulting. No reactive cells were observed in PBMCs and EBV-specific CTLs for all 3 donors. The frequency of YLQ peptide–reactive LMP1-specific CTLs was 3.82% for donor A, 0.52% for donor B, and 0.55% for donor C. YLQ peptide–reactive CTLs were undetectable in PBMCs and EBV-specific CTLs.