Figure 1.

Induction of long-lived increased CTLp frequencies with GP2.9 cells. Mice were immunized i.p. with irradiated (2500 cGy) GP2.9 cells (3 × 10⁶ cells) (solid triangles) or left untreated (open squares). At the indicated time points, spleen cells were restimulated for 5 days in vitro and tested in a conventional ⁵¹Cr release assay on EL-4 cells pulsed with the relevant peptide (Upper). Alternatively, mice were challenged i.v. with LCMV (strain WE, 200 pfu), and virus titers in spleens were determined 5 days later (Lower). The horizontal line indicates the detection limit. The number of points below the line indicates the number of mice with no detectable virus. One representative experiment of two is shown.