Our present results indicate an active induction of Treg by the parasite as follows: (i) Using an in vivo infection model for secondary AE (8, 14–16, 38, 39, 47), we observed a significant expansion of Foxp3 + Treg over effector T-cells in the peritoneum of mice in a time window around 7 days post infection. Here, FOXP3 is linked to infection.