Macrophages are required for in vivo Th17 expansion and induction of arthritis. (A) Specific depletion of macrophages in SKG mice 3 d after i.v. injection of 200 µl CL. One representative out of three independent experiments is shown (numbers indicate percentages). (B) Joint scores of SKG mice i.v. injected with 200 µl PBS or CL 1 d before mannan treatment. *, P < 0.05. Error bars are means ± SD. (C) Percentage of IL-17⁺ CD4⁺ T cells in the popliteal lymph nodes of SKG mice 2 wk after mannan treatment. Mice were pretreated by an i.v. injection of PBS or CL (n = 6). Horizontal bars are the means.