Transforming growth factor type ?1(TGF—?1)belong to a family of polypeptides with regulato-ry effects on growth and differention of a variety of cells types.TGF—?1 play an important rolein regulation of immune response by acting as a negative modulate the cell proliferation throughstill unknow mechanisms.We investigated the effect of TGF—?1 on the IL—2R expression andproliferation activited DN cells and we observed that TGF—?1 was able to increase the expres-sion of IL—2R in DN cells and to suppress the proliferation of DN cells and we have discussedabout these results.