FOXP3 and Sepsis: This also explains the effect of TGF‐β1 on Foxp3+Tregs function. Xiao et al.33also observed that all‐trans retinoic acid (ATRA) enhanced Smad3 expression and phosphorylation that resulted in increased differentiation of Tregs. In this study, we demonstrated that Smad3 was the key factor in stabilizing CD4+CD25+ Tregs mediated by recombinant TGF‐β1 during sepsis.