FIG. 5.

Transfer of immune CD8⁺ T cells affects IFN-γ production by CD4⁺ T cells. CD8⁺ T cells were purified by positive selection from the spleens of H-2^a/a mice at 8 days postvaccination with FV-N. More than 95% of these cells were positive for both CD8 and CD3, as analyzed by flow cytometry. Approximately 1.5 × 10⁷ CD8⁺ T cells from FV-N-vaccinated or unvaccinated H-2^a/a mice were transferred to each naive H-2^a/a mouse. As an additional control, a similar number of CD8⁻ cells were also transferred to naive H-2^a/a mice. At day 1 posttransfer, all groups were infected with 15 SFFU of FV-B. At 8 days postinfection, CD4⁺ T cells were purified and analyzed for IFN-γ production as described for Fig. 1. Data shown are the average values + SEM for four to eight mice per group and are the combined results from two separate experiments.