The frequency of CMV-specific CTL precursors is preserved after IL-2 and IL-7 prestimulations. The frequency of pp65-specific CD8⁺ T-cell precursors was measured for each culture condition as described in “Materials and methods.” PBMCs and cells at day 9 of culture were stimulated in limiting dilution numbers with autologous cells pulsed with the pp65_495-503 peptide. A ⁵¹Cr release assay was performed 10 days later. Regression curves were interpolated, and precursor frequencies were determined according to Poisson statistics. Precursor frequencies are shown.