Chromium release assay examining the expression of the E6 52–61 CD8 T cell epitope by primary tumor cell lines derived from cervical cancer patients. The cells were untreated (upper left), treated with IFN-γ (upper right), pulsed with the E6 52–61 peptide (middle left), pulsed with the peptide and treated with IFN-γ (middle right), infected with E6-vac (lower left), or infected with E6-vac and treated with IFN-γ (lower right). Assays were performed in triplicate wells, with error bars representing the standard error of the means. A representative experiment, of two experiments performed, is shown.