FIG. 6.

The LCMV-induced attrition of CD8β⁺ CD44^high T cells correlates with a substantial increase in DNA fragmentation and caspase 3 activation but not annexin V reactivity. C57BL/6 mice were infection with LCMV-Armstrong i.p. Splenocytes were harvested at 0, 1, 2, 3, and 4 days postinfection. DNA fragmentation was assessed via TUNEL staining after a brief in vitro culture of splenocytes for 5 h at 37°C (see Materials and Methods). (A) Annexin V and CD11c staining on CD8α⁺ CD44^high and CD8β⁺ CD44^high cells at days 0,1, and 2 after LCMV infection. Histogram inset in quadrant 3 show CD40 expression on the annexin V⁺ CD11c⁺ CD8α⁺ CD44^high population (quadrant 2). (B) Absolute CD8β⁺ CD44^high T cell numbers at 0, 1, 2, 3, and 4 days postinfection. Error bars indicate standard deviations. (C) Histogram overlays depicting CD8β⁺ CD44^high annexin V reactivity and caspase 3 activation on days 0, 1, 2, 3, and 4 after LCMV infection. Line color corresponds to day after LCMV infection. (D) Percentages of TUNEL⁺ CD8β⁺ CD44^high T cells isolated from mice at days 0, 1, 2, 3, and 4 postinfection. Absolute numbers were based upon percentages obtained via flow cytometry. The data are representative of three independent experiments with three mice per group..