The results showed that the proportion of Th9 cells in the IL-17 and SSc serum groups was significantly higher than that in the control group; however, the proportion of Th9 cells in the IL-17 neutralizing antibody group was significantly lower than that in the control group and IL-17 neutralizing antibody decreased the promoting effect of serum on Th9 cells (Fig. 5A). This evidence concerns the gene IL17A and systemic sclerosis.