IL‐17 more than IFN‐γ is required for the progression of arthritis in PIA. (A–D) Neutralizing antibodies to IFN‐γ (DB‐1) and IL‐17 (17F3) were injected i.v. into rats at day 8, 10, 12, and 14 after pristane administration using MOPC‐21 as an isotype control. Disease development (left) and weight change (% versus day of onset, right) are shown for DA (A), DA.1FR9 (B), DA.1HR10 (C) and DA.1UR10 (D); n = 8–11 per group as indicated in figures, *p < 0.05; **p < 0.01; ***p < 0.001 (compared to isotype); p‐values for trend in (B) and (D) represent differences between DB‐1 and MOPC‐21 (All data in A–D was analyzed by Mann‐Whitney). (E) Frequencies (gates in dot plots) and numbers (scatter plot) of CD11 b/c+ CD8a‐ polymorphonuclear leukocytes (PMNs) in blood were determined in rats shown in (A) at day 16 post pristane injection; ***p < 0.001 (compared to isotype and DB‐1, Mann–Whitney). Data shown in A–D are pooled from two independent experiments with similar results. Error bars in (A–D) represent SEM; vertical line and error bars in (E) represent mean and standard deviation, respectively.