IL17A and systemic sclerosis: Furthermore, we showed that supernatants from Th17 cells of patients with active SSc induced more collagen 1 and collagen 3 production in fibroblasts than did supernatants of Th17 cells from healthy controls (Figure 5A, B), and neutralization of IL-17 in the culture medium inhibited mRNA expression and protein secretion of collagen 1 and collagen 3.