The TGF-β1 and PDGF-BB produced by Tregs promote lesional growth, EMT, FMT, and fibrosis in endometriosis, while the IL-33 secreted by endometriotic cells transform Tregs into Th2-like Tregs, producing more profibrotic cytokines IL-13 [66], IL-4, and even TGF-β1. The gene discussed is IL4; the disease is endometriosis.