CD4 and neoplasm: Moreover, TGF-β1 promotes survival of post-thymic naïve CD4+ T lymphocytes to later promote CD4+CD25+ Treg differentiation from uncommitted peripheral CD4+ cells via FOXP3 and Smad3, while preventing its differentiation into the Th-1 and Th-2 effector cell, thereby leading to tumor cell tolerance [109,110,111].