IL-23-treated neutrophils promote dextran sulfate sodium (DSS)-induced colitis in IL-17 knockout (KO) recipients. DSS (2.5%) was administered to IL-17A KO mice for colitis induction. PBS, 5 × 106 untreated or IL-23-treated neutrophils (sorted CD11b+Ly6G+ neutrophils) per mouse were i.v.-injected on days 0, 2 and 5. The survival rate (a), body weight (b), macroscopic score (c) and representative colon pictures (d) of control and DSS-induced colitis mice are shown. (e) H&E staining of colonic tissues from control or DSS-induced colitis mice treated as described above are presented. The mRNA expression levels of IL-17A (f) and IL-22 (g) in colonic tissues from mice treated as described above were detected by real-time PCR. Data are expressed as the mean±s.d. (n=3–5) and one representative example from three independent experiments with similar results is shown. *P<0.05, **P<0.01 and ***P<0.001 for comparisons between the indicated groups. Data were analyzed by the Mann–Whitney U-test or two-way ANOVA using SPSS software. Survival curves were analyzed by the log-rank test.