The TGF-β–induced Smad3 phosphorylation in PBLs from patients with SSc (Fig. 3b, left panel) was decreased in the presence of a specific Smad3 inhibitor (SIS3), although to a lesser extent than the decrease observed in T lymphocytes from healthy donors and in Jurkat T cells (Fig. 3b, middle and right panels, respectively). Here, TGFB1 is linked to systemic sclerosis.