Tgf-β1 produced by activated CD4+ T Cells Antagonizes T Cell Surveillance of Tumor Development

TGF beta 1 is a regulatory cytokine with a crucial function in the control of T cell tolerance to tumors. Our recent study revealed that T cell-produced TGF beta 1 is essential for inhibiting cytotoxic T cell responses to tumors. However, the exact TGF beta 1-producing T cell subset required for tumor immune evasion remains unknown. Here we showed that deletion of TGF beta 1 from CD8(+) T cells or Foxp3(+) regulatory T (Treg) cells did not protect mice against transplanted tumors. However, absence of TGF beta 1 produced by activated CD4(+) T cells and Treg cells inhibited tumor growth, and protected mice from spontaneous prostate cancer. These findings suggest that TGF beta 1 produced by activated CD4(+) T cells is a necessary requirement for tumor evasion from immunosurveillance.