FIG. 1.

Detection of low frequencies of K^bS-specific CD8⁺ T cells. Single-cell suspensions of splenocytes were incubated for 5 h in medium alone or with either the K^bOVA peptide or K^bS peptide, as indicated in the dot plots. BFA was included for the final 4 h of incubation. The cells were gated for the expression of TCRβ, and IFN-γ expression within the TCRβ⁺ CD8⁺ population was examined. The data shown are for a mouse that was immunized 14 days previously with plasmid pCI/S. Similar results were obtained in seven independent experiments in which a total of over 60 pCI/S-immunized and 12 control (6 pCI/C-immunized and 6 naïve mice) mice were examined. Over 100,000 TCRβ⁺ CD8⁺ cells are shown in each case. The percentage of cells within the indicated gate is shown for each restimulation. All axes represent log fluorescence intensities. Staining with an appropriate isotype control monoclonal antibody (MAb) did not result in cells within the indicated gate (data not shown).