FIG. 4.

Primary cytotoxicity of CD8⁺ peritoneal exudate cells from TAg-immunized mice after depletion of CD4⁺ cells at different times during immunization or maturation. Mice were immunized on days −14 and −7 by i.p. injection of 10 μg of TAg and challenged on day 0 with 10⁶ mKSA cells injected i.p. Depletion of CD4⁺ cells was achieved by treating groups of five mice on days −15 and −8, day −1, day +2, or day +5 with an i.v. injection of CD4-specific MAb. On day 8, the cytotoxic activity of CD8⁺ peritoneal exudate cells was determined with a standard 4-h chromium release assay using mKSA cells as targets. Variable effector/target ratios are due to various yields of CD8⁺ TAL in the groups.