FIG. 2.

Role of CD28 costimulation for the generation of protective CD4 and CD8 T-cell responses. Mice were vaccinated subcutaneously twice with 10⁴ live yeast at each site of injection. To induce protective CD8 T-cell immunity, CD28^−/− and wild-type mice were depleted by anti-CD4 MAb throughout the experiment. Mice were infected with 2 × 10³ wild-type yeast and analyzed for lung CFU 14 to 16 days after infection. The data are geometric mean CFU ± the standard error of the mean of two independent experiments; n = 8 to 12 mice/group. *, P < 0.001 (versus unvaccinated controls); **, P < 0.001 (versus corresponding vaccinated CD28^−/− mice); ***, P < 0.005 (versus corresponding CD4-depleted mice).