In normal mice, treatment with rTsPmy increased only CTLA4 in CD4+Foxp3– T cells (data not shown), not in CD4+Foxp3+ T cells, which is consistent with the results of infections with H. polygyrus, Strongyloides ratti, Brugia malayi, and Litomosoides sigmodontis (Finney et al., 2007; Taylor et al., 2007; Walsh et al., 2007; McSorley et al., 2008). Here, CTLA4 is linked to infection.