p11C, C-M-specific CTL responses 4 weeks after the SIVmac challenge (week 49). PBLs were isolated, restimulated in vitro, and tested on peptide-unpulsed (the first bar for each animal) or pulsed (the last three bars for each animal) PBLs for cytolytic activity as described in the legend to Fig. 1. The effector/target ratios were 25:1, 12:1, and 6:1.