Impaired CTL cytotoxicity determines loss of virus control in souris mice. (A-B) CD8 T cells were isolated from spleens of wild-type, souris, and beige^J mice that had been infected with 200 pfu LCMV 8 days before. A total of 2 × 10⁶ MACS-purified CD8⁺ T cells were transfused into wild-type C57BL/6 mice that had been infected with 10⁴ pfu LCMV 10 hours before; and after additional 18 hours, LCMV titers were determined in the spleen. (B) Pooled data for 3 to 5 individual mice per group from 2 independent experiments. (C-D) Spleen cells from wild-type, souris, and beige^J P14 mice were incubated with gp33 for 3 days and adoptively transfused into C57BL/6 recipients. Twenty-four hours later, mice were challenged with 200 pfu LCMV; and 3 days later, LCMV titers were determined in the spleen. Nil indicates the control group without transfused cells. The dashed line indicates the detection limit.