These levels were not significantly different from those detected in healthy donors, but TGF-β induced a significant increase in the percentages of IL-13-producing CD4+ T cells (Fig. 1b) and of IL-13-producing CD8+ T cells (Fig. 1c) from patients with SSc, with respective mean fold increases of 1.6 ± 0.05 and 2.7 ± 0.02 (n = 7; p < 0.05 and p < 0.001, respectively). Here, CD4 is linked to systemic sclerosis.