TGFB1 and neoplasm: TGF-β promotes the development of naïve CD4+ T cells into Tregs, which maintain immunological tolerance and suppress anti-tumor immunity.312 For example, TGF-β signaling is crucial for the early thymic development of natural CD4+CD25+Foxp3+Tregs, as evidenced by the absence of these cells after conditional deletion of the TGF-β receptor I in T cells.