Smad3 is involved in TGF-β-mediated the up-regulation of IL-21-producing cells.

<p>Naïve CD4⁺ T cells from CBMCs were stimulated for 2 d with immobilized anti-CD3 and anti-CD28 mAbs (neutral condition), rested overnight and re-stimulated for 15 min with or without IL-21, TGF-β or IL-21 plus TGF-β. A. The cells were lysed and subjected to western blotting. A single membrane and phosphotyrosine specific antibodies had been used. The total Smad3 were as the positive controls. Data were representative of three separate experiments with similar results. B. The ratio of pSmad3 to tSmad3 was quantified by desitometry, and statistical data shown were mean±SD from three independent experiments as described in A. P<0.05 was considered significant.