IL17F and systemic sclerosis: However, a trend was observed for IL-17F, with 3 out of 4 lSSc having an IL-17F frequency higher than the 75 percentile of those of dSSc individuals (Figure 1B) The expression pattern of these IL-17 isoforms was specific to SSc, since the frequency of IL-17A+ and IL-17F + cells identified in the skin of 5 morphea patients was similar to that found in HD skin (Figure 1A and B).