Cytolytic activity of Tc1 and Tc2 clones generated from PBMC of HIV-seronegative subjects. T-cell blasts of 22 representative CD8 T-cell clones (11 Tc1, ○ and 11 Tc2, •) were incubated at four different effector/target ratios (4:1; 2:1; 1:1; 1:2) in triplicate with 5 × 10^3 51Cr-labeled P815 mastocytoma cells for 4 hours at 37°C in the presence of anti-CD3 Ab (100 ng/mL). The ⁵¹Cr release for each clone was calculated as described in Materials and Methods. The mean values (±SE) of specific cytolytic activity at each E/T ratio of Tc1 (◃ ) and Tc2 (◂ ) clones are also reported.