Transforming growth factor-beta1 gene transfer is associated with the development of regulatory cells

Adenovirus-mediated transfection of mouse cardiac allografts with active human transforming growth factor-beta 1 (TGF-beta 1) prolongs transplant survival provided that recipients are initially depleted of CD8+ T cells. To test if graft survival was prolonged by persistent TGF-beta 1 transgene expression, long-term transfected allografts were re-transplanted into naive mice that were transiently depleted of CD8+ T cells. Re-transplanted allografts were acutely rejected, indicating that TGF-beta 1 transgene expression did not suppress effector cell function. We next asked whether TGF-beta 1 gene transfer was associated with the development of regulatory cells. When splenocytes obtained from mice bearing long-term TGF-beta 1-transfected allografts were adoptively transferred into recipients of non-transfected cardiac allografts, prolonged allograft survival was observed, and increased levels of the regulatory T cell transcription factor Foxp3 were present. To further test for regulation, differentiated effector cells were obtained from mice that had rejected cardiac allografts and were adoptively transferred into mice bearing long-term TGF-beta 1 transfected cardiac allografts. The effector cells failed to mediate rejection in mice bearing TGF-beta 1-transfected allografts and we observed a significant increase in intra-graft Foxp3 expression. These findings indicate that TGF-beta 1 gene transfer allows for the development of regulatory cells that control graft-reactive T cell responses once therapeutic levels of the transgene product are no longer produced.