Analysis of T-cell frequencies by tetramer. Frequencies of (A) TDL- and (B) TYF-specific T cells in PBMCs and CTL lines following one Ad stimulation. PBMCs (day 0) and CTL lines (day 9) from A*1-positive (3 and 4) and A*24-positive donors (8 and 9) were screened for the percentage of tetramer-positive T cells.