Increased apoptosis of CD8⁺ T cells in the brain of <i>Il21</i>^−/− mice during chronic toxoplasmic encephalitis.

<p>A) The percentage of CD4⁺ (left) and CD8⁺ (right) T cells expressing Bcl-2 in the brain of individual WT and <i>Il21</i>^−/− mice infected for 35 days. Bar graph represents the total number of Bcl-2⁺ CD4⁺ and CD8⁺ T cells in the brain of WT and <i>Il21</i>^−/− mice infected for 35 days. B) Flow cytometry of BMNCs from WT and <i>Il21</i>^−/− mice infected for 35 days and then stained for the early apoptotic marker Annexin V. Numbers above line indicate percent Annexin V⁺CD4⁺ (left) or Annexin V⁺CD8⁺ (right) T cells in the brain of chronically infected WT and <i>Il21</i>^−/− mice. Bar graph represents the total number of Annexin V⁺ CD4⁺ and CD8⁺ T cells in the brain of WT and <i>Il21</i>^−/− mice infected for 35 days. Data are representative of two independent experiments with similar results. Error bars represent SEM. Significance was determined by a two-tailed unpaired Student’s <i>t</i> test. *<i>P</i><0.05, **<i>P</i><0.01.