We isolated CD4+CD25+FOXP3+ Tregs from endometriotic lesions as well as normal endometrial (NE) tissues from women without endometriosis and evaluated, by flow cytometry, the proportion of Tregs that were also positive for Tregs/Th1/Th2-associated cytokines (TGF-β1, IL-10, IFN-γ, and IL-4 and IL-13) and ST2 (an IL-33 receptor). Here, FOXP3 is linked to endometriosis.