Mannan triggers autoimmune arthritis by expanding Th17 cells. (A) Joint score of 8∼12-wk-old SKG or BALB/c mice that received a single i.p. injection of mannan at the indicated doses. A total of two independent experiments are shown. Error bars are means ± SD of scores. (B–E) A representative joint swelling and histology of an SKG (B and D) and a BALB/c mouse (C and E) 8 wk after mannan treatment (hematoxylin and eosin staining). Bars, 200 µm. (F) Joint scores of IL-17^+/+ or IL-17^−/− SKG mice 8 wk after mannan treatment (n = 12). Horizontal bars are the means of each group. (G) Intracellular staining of IL-17 and IFN-γ in CD4⁺ T cells in the popliteal lymph nodes from SKG or BALB/c mice 8 wk after mannan treatment (numbers indicate percentages). One representative staining out of six independent experiments is shown. (H) Percentages of IL-17⁺ cells in CD4⁺ T cells in each SKG or BALB/c group (n = 6), as shown in G. Horizontal bars are the means of each group.