Wild type mice were infected as in figure 3. Groups of mice were injected i.p on days (0–3), (3–6), or (4–6), with 150 µg of either control IgG or anti-B7.2 blocking antibody in PBS as indicated. At day 7 post-infection splenocytes were harvested and stained for CD8, CD44, B8R-tetramer. Representative plots of B8R-tetramer staining, gating on CD8 T cells is shown. Percentages of B8R-tetramer positive CD8 T cells (CD8+CD44+B8R+) are indicated. Similar results were obtained in 2 separate experiments.