Compared with the control group, IL-17 levels in both plasma and colon tissue were greater in the colitis group (P <0.05; Figures 3A, 3B and 3C–G), and were only decreased by the culture supernatant of F. prausnitzii (P <0.05; colitis vs. supernatant groups; Figures 3A, 3B and 3C–G). This evidence concerns the gene IL17A and colitis.