Here, we demonstrate that AS1517499 treatment during acute colitis prevents the decline in the frequency of CD4+Foxp3+ Tregs (Fig. 6D) and promotes the maintenance of activated Treg subsets, including CD4+Foxp3+CD25+ cells (Fig. 6E), IFN-γ–expressing Tregs (CD4+Foxp3+IFN-γ+; Fig. 6 F), and PD-1–expressing Tregs (CD4+Foxp3+PD-1+; Fig. 6G). This evidence concerns the gene PDCD1 and colitis.