Treatment with anti-IL-17 antibody prevents CIA in IFN-γR KO mice. (a) Interferon-γ receptor knock-out (IFN-γR KO) and wild-type mice were immunized with collagen type II (CII) in complete Freund's adjuvant (in vivo). At day 21 post immunization, five IFN-γR KO and six wild-type mice were challenged with 10 μg anti-CD3 antibody and serum levels of IL-17 were determined 1.5 hours later. Bars represent averages ± standard error of the mean (SEM). In vitro: lymph nodes were isolated at day 35 post immunization, and lymphocytes were stimulated with 3 μg/ml anti-CD3 antibody. Supernatants were collected after 72 hours and tested for IL-17 expression. Bars represent averages ± SEM of triplicate cultures. * P < 0.05 for comparison with IFN-γR KO mice (Mann-Whitney U-test). (b, c) Immunized IFN-γR KO mice were injected with anti-IL-17 or control antibody. (b) Cumulative incidence of arthritis and (c) mean arthritic score of mice are shown. Error bars indicate SEM. Data are representative for three independent experiments. * P < 0.05 (day 19) and 0.005 (from day 20 onwards) for comparison with control-treated mice (Mann-Whitney U-test). (d) The mean arthritic score on day 21 of arthritic mice only is shown for three experiments. Error bars indicate SEM. The number of arthritic mice to the total number of mice in each group is shown in brackets.