FIG. 7.

Virus-specific CD8⁺ T cells in nonlymphoid tissues during chronic infection preserve the ability to up-regulate lytic activity after antigenic stimulation in vitro. C57BL/6 mice were infected with 10² (A) or 2 × 10⁶ (B) PFU of LCMV-Docile, and lymphocytes isolated from the spleen and liver at the indicated times after infection were stimulated with virus-infected macrophages as described in Materials and Methods. The cytolytic activity of restimulated lymphocytes cultured at a density of 4 × 10⁶/well was measured in a ⁵¹Cr release assay using virus-infected MC57G cells (•) or EL-4 cells loaded with peptide GP133-41 (▴) or NP396-404 (▪) as a target. Cultured cells were resuspended in 1 ml of medium per culture well, and serial threefold dilutions of effector cells were performed. E:T cell ratios shown in the blot are corrected for the total number of tetramer-positive cells per culture well of the original lymphocyte populations (prior to culture), as described in Materials and Methods. Results are representative of three separate experiments.