TGFB1 and neoplasm: One such study described the suppressive effects of TGF-β1 on the production of the anti-tumor cytokines, interleukin (IL)-2 and interferon (IFN)-γ, via mechanisms that were attributed to a decreased expression of the lineage-determining, pro-Th1 differentiation factor, T-bet (T-box transcription factor 21, TBX21) [29].