The previous studies that Il21r−/− mice infected with T. gondii survive to 100 days post-infection without showing any sign of increased susceptibility [11], are incongruous with a role for IL-21 in the induction of IL-10, TFH cell development or B cell responses [15], [16], [19], [21], [22], as well as the maintenance of effector CD8+ T cell responses [18], [24], [25]. This evidence concerns the gene CD8A and infection.