Figure 1.

Effect of CTLA-4 blockade on the response to immunization. BALB/c mice received anti-HA TCR transgenic T cells on day 0 and were treated with the anti-CTLA-4 antibody 9H10 (100 μg/day, i.p.) on days −1, 0, and +1 or received no treatment. On day +2 after T cell transfer half the mice in each group were immunized with vacc-HA, and 6 days later, T cells were isolated as described in Materials and Methods. Data represent the combined results of two independent experiments (three mice per group per experiment). Each point represents the value for an individual animal. Horizontal lines and the numbers indicate the average for six mice in each group. (A) Percentage of CD4⁺ anti-HA TCR⁺ cells as determined by FACScan analysis. (B) Proliferative response to stimulation with HA peptide in vitro. Data are shown as cpm from which values for medium alone were subtracted. (C) Production of IFN-γ in response to stimulation with HA peptide. Values for T cells cultured in medium alone were zero. (D) Proliferative response to stimulation with splenocytes infected with wild-type vaccinia virus. [³H]Thymidine incorporation was determined after 3 days in culture. Data are shown as cpm from which values for medium alone were subtracted.